| Conditions | 41 | 
| Total Lines | 274 | 
| Code Lines | 183 | 
| Lines | 0 | 
| Ratio | 0 % | 
| Changes | 0 | ||
Small methods make your code easier to understand, in particular if combined with a good name. Besides, if your method is small, finding a good name is usually much easier.
For example, if you find yourself adding comments to a method's body, this is usually a good sign to extract the commented part to a new method, and use the comment as a starting point when coming up with a good name for this new method.
Commonly applied refactorings include:
If many parameters/temporary variables are present:
Complex classes like indexResourceHook.ts ➔ useResourceIndex often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
| 1 | import { | 
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| 95 | |||
| 96 | /**  | 
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| 97 | * This hook keeps a local list of entities in sync with a REST api representing a single resource.  | 
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| 98 | *  | 
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| 99 | * *** Interaction with API ***  | 
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| 100 | * The API can be interacted with in 4 ways:  | 
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| 101 | * - Refreshing, getting a complete list of entities  | 
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| 102 | * - Creating a new entity that is added to the list  | 
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| 103 | * - Updating a specific entity in the list  | 
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| 104 | * - Deleting a specific entity in the list  | 
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| 105 | *  | 
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| 106 | * The only required argument is the API endpoint. By default, the CRUD operations (Create, Read, Update, Delete) follow normal REST conventions:  | 
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| 107 | * - Create submits a POST request to endpoint  | 
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| 108 | * - Refresh submits a GET request to endpoint  | 
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| 109 | * - Update submits a PUT request to endpoint/id  | 
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| 110 | * - Delete submits a DELETE request to endpoint/id  | 
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| 111 | * The urls used may be modified by overriding resolveEntityEndpoint (for update and delete requests) and resolveCreateEndpoint.  | 
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| 112 | * This may allow, for example, for using query parameters in some of these urls.  | 
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| 113 | * Note: The HTTP verbs used cannot be changed.  | 
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| 114 | *  | 
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| 115 | * The api requests MUST return valid JSON (except for delete requests), or the request will be considered to have failed.  | 
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| 116 | * The response to refresh requests must be a JSON List, and update and create requests must return the resulting entity as a json object.  | 
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| 117 | * However, the JSON objects may be preprocessed before being stored locally, by overriding parseEntityResponse and/or parseIndexResponse.  | 
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| 118 | *  | 
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| 119 | * *** Hook Values and Statuses *** *  | 
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| 120 | * values: This represents the list of entities compressing the resource.  | 
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| 121 | * Note: values is not an array. It is an object with each entity indexed by id, so specific items may be retrieved more easily.  | 
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| 122 | * Note: By default, values starts out empty and the hook immediately triggers a refresh callback.  | 
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| 123 | * Note: An initialValue may be provided, which suppresses that initial refresh, unless forceInitialRefresh is ALSO overridden with true.  | 
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| 124 | * Note: Setting forceInitialRefresh to false has no effect. Set initialValue to [] instead.  | 
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| 125 | *  | 
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| 126 | * indexStatus, createStatus, and entityStatus: These tell you whether any requests are currently in progress, and if not whether the last completed request was successful.  | 
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| 127 | * Note: entityStatus covers both update and delete requests, and contains a status value for each entity, indexed by id.  | 
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| 128 | *  | 
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| 129 | * *** Callbacks *** *  | 
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| 130 | * create, refresh, update, deleteResource: These callbacks trigger requests to the api, updating values and the status properties accordingly.  | 
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| 131 | * Note: while conventional "reactive" programming would control UI based only on the current values and status properties, these callbacks also return promises  | 
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| 132 | * which allow code to respond to the success or failure of specific requests.  | 
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| 133 | *  | 
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| 134 | * *** Error Handling ***  | 
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| 135 | * You may watch for statuses of "rejected" to determining whether an error occurred during certain requests.  | 
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| 136 | * To respond to any details of potential errors, override handleError.  | 
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| 137 | * Note: If the error was caused by a non-200 response from the server, handleError will receive an instance of FetchError, which contains the entire response object.  | 
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| 138 | */  | 
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| 139 | export function useResourceIndex<T>(  | 
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| 140 | endpoint: string, // API endpoint that returns a list of T.  | 
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| 141 |   overrides?: { | 
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| 142 | initialValue?: T[]; // Defaults to an empty list.  | 
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| 143 | skipInitialRefresh?: boolean; // Defaults to false. Override if you want to keep the initialValue until refresh is called manually.  | 
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| 144 | parseEntityResponse?: (response: Json) => T; // Defaults to the identity function.  | 
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| 145 | parseIndexResponse?: (response: Json) => T[]; // Defaults to (response) => response.map(parseEntityResponse)  | 
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| 146 | resolveEntityEndpoint?: (baseEndpoint: string, entity: T) => string; // Defaults to appending '/id' to baseEndpoint. Used for update (PUT) and delete (DELETE) requests.  | 
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| 147 | resolveCreateEndpoint?: (baseEndpoint: string, newEntity: T) => string; // Defaults to identical to endpoint. Used for create (POST) requests.  | 
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| 148 | handleError?: (error: Error | FetchError) => void;  | 
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| 149 | keyFn?: (item: T) => string | number; // Returns a unique key for each item. Defaults to using `item.id`.  | 
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| 150 | },  | 
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| 151 | ): { | 
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| 152 | values: IndexedObject<T>;  | 
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| 153 | initialRefreshFinished: boolean; // If an initial refresh happens, this becomes true after is fulfilled or rejected. If initial fetch is skipped, this will be true immediately.  | 
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| 154 | indexStatus: ResourceStatus; // The state of any requests to reload the entire index.  | 
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| 155 | createStatus: ResourceStatus; // If ANY create requests are in progress, this is 'pending'. Otherwise, it is 'fulfilled' or 'rejected' depending on the last request to complete.  | 
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| 156 | entityStatus: IndexedObject<ResourceStatus>; // Note that if indexStatus is 'pending', every entity status will also be 'pending'.  | 
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| 157 | create: (newValue: T) => Promise<T>;  | 
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| 158 | refresh: () => Promise<T[]>; // Reloads the entire index.  | 
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| 159 | update: (newValue: T) => Promise<T>;  | 
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| 160 | deleteResource: (value: T) => Promise<void>;  | 
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| 161 | } { | 
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| 162 | const initialValue = overrides?.initialValue ?? [];  | 
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| 163 | const doInitialRefresh = overrides?.skipInitialRefresh !== true;  | 
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| 164 | const parseEntityResponse = overrides?.parseEntityResponse ?? identity;  | 
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| 165 | const parseIndexResponse = useMemo(  | 
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| 166 | () =>  | 
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| 167 | overrides?.parseIndexResponse ??  | 
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| 168 | ((response: Json): T[] => response.map(parseEntityResponse)),  | 
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| 169 | [overrides?.parseIndexResponse, parseEntityResponse],  | 
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| 170 | );  | 
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| 171 | const resolveEntityEndpoint =  | 
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| 172 | overrides?.resolveEntityEndpoint ?? defaultEntityEndpoint;  | 
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| 173 | const resolveCreateEndpoint =  | 
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| 174 | overrides?.resolveCreateEndpoint ?? defaultCreateEndpoint;  | 
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| 175 | const handleError = overrides?.handleError ?? doNothing;  | 
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| 176 | const keyFn = overrides?.keyFn ?? defaultKeyFn;  | 
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| 177 | |||
| 178 | const addKey = useCallback(  | 
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| 179 |     (item: T): { item: T; key: string | number } => { | 
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| 180 |       return { item, key: keyFn(item) }; | 
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| 181 | },  | 
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| 182 | [keyFn],  | 
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| 183 | );  | 
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| 184 | |||
| 185 | const isSubscribed = useRef(true);  | 
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| 186 | |||
| 187 | const [state, dispatch] = useReducer<  | 
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| 188 | Reducer<ResourceState<T>, AsyncAction<T>>  | 
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| 189 | >(  | 
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| 190 | indexCrudReducer,  | 
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| 191 | initializeState(initialValue.map(addKey), doInitialRefresh),  | 
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| 192 | );  | 
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| 193 | |||
| 194 | const values = useMemo(() => valuesSelector(state), [state]);  | 
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| 195 |   const { initialRefreshFinished } = state.indexMeta; | 
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| 196 | const indexStatus = state.indexMeta.status;  | 
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| 197 | const createStatus = state.createMeta.status;  | 
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| 198 | const entityStatus = useMemo(() => statusSelector(state), [state]);  | 
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| 199 | |||
| 200 | const create = useCallback(  | 
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| 201 |     async (newValue: T): Promise<T> => { | 
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| 202 |       dispatch({ | 
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| 203 | type: ActionTypes.CreateStart,  | 
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| 204 |         meta: { item: newValue }, | 
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| 205 | });  | 
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| 206 | let entity: T;  | 
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| 207 |       try { | 
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| 208 | const json = await postRequest(  | 
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| 209 | resolveCreateEndpoint(endpoint, newValue),  | 
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| 210 | newValue,  | 
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| 211 | ).then(processJsonResponse);  | 
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| 212 | entity = parseEntityResponse(json);  | 
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| 213 |         if (!isValidEntity(entity)) { | 
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| 214 | throw new Error(UNEXPECTED_FORMAT_ERROR);  | 
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| 215 | }  | 
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| 216 |       } catch (error) { | 
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| 217 |         if (isSubscribed.current) { | 
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| 218 |           dispatch({ | 
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| 219 | type: ActionTypes.CreateReject,  | 
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| 220 | payload: error,  | 
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| 221 |             meta: { item: newValue }, | 
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| 222 | });  | 
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| 223 | handleError(error);  | 
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| 224 | }  | 
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| 225 | throw error;  | 
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| 226 | }  | 
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| 227 |       if (isSubscribed.current) { | 
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| 228 |         dispatch({ | 
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| 229 | type: ActionTypes.CreateFulfill,  | 
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| 230 | payload: addKey(entity),  | 
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| 231 |           meta: { item: newValue }, | 
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| 232 | });  | 
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| 233 | }  | 
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| 234 | return entity;  | 
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| 235 | },  | 
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| 236 | [endpoint, resolveCreateEndpoint, parseEntityResponse, handleError, addKey],  | 
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| 237 | );  | 
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| 238 | |||
| 239 |   const refresh = useCallback(async (): Promise<T[]> => { | 
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| 240 |     dispatch({ | 
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| 241 | type: ActionTypes.IndexStart,  | 
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| 242 | });  | 
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| 243 | let index: T[];  | 
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| 244 |     try { | 
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| 245 | const json = await getRequest(endpoint).then(processJsonResponse);  | 
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| 246 | index = parseIndexResponse(json);  | 
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| 247 |       if (!isValidEntityList(index)) { | 
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| 248 | throw new Error(UNEXPECTED_FORMAT_ERROR);  | 
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| 249 | }  | 
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| 250 |     } catch (error) { | 
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| 251 |       if (isSubscribed.current) { | 
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| 252 |         dispatch({ | 
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| 253 | type: ActionTypes.IndexReject,  | 
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| 254 | payload: error,  | 
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| 255 | });  | 
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| 256 | handleError(error);  | 
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| 257 | }  | 
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| 258 | throw error;  | 
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| 259 | }  | 
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| 260 |     if (isSubscribed.current) { | 
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| 261 |       dispatch({ | 
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| 262 | type: ActionTypes.IndexFulfill,  | 
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| 263 | payload: index.map(addKey),  | 
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| 264 | });  | 
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| 265 | }  | 
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| 266 | return index;  | 
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| 267 | }, [endpoint, parseIndexResponse, handleError, addKey]);  | 
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| 268 | |||
| 269 | const update = useCallback(  | 
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| 270 |     async (newValue: T): Promise<T> => { | 
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| 271 | const meta = addKey(newValue);  | 
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| 272 |       dispatch({ | 
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| 273 | type: ActionTypes.UpdateStart,  | 
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| 274 | meta,  | 
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| 275 | });  | 
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| 276 | let value: T;  | 
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| 277 |       try { | 
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| 278 | const json = await putRequest(  | 
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| 279 | resolveEntityEndpoint(endpoint, newValue),  | 
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| 280 | newValue,  | 
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| 281 | ).then(processJsonResponse);  | 
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| 282 | value = parseEntityResponse(json);  | 
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| 283 |         if (!isValidEntity(value)) { | 
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| 284 | throw new Error(UNEXPECTED_FORMAT_ERROR);  | 
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| 285 | }  | 
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| 286 |       } catch (error) { | 
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| 287 |         if (isSubscribed.current) { | 
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| 288 |           dispatch({ | 
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| 289 | type: ActionTypes.UpdateReject,  | 
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| 290 | payload: error,  | 
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| 291 | meta,  | 
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| 292 | });  | 
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| 293 | handleError(error);  | 
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| 294 | }  | 
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| 295 | throw error;  | 
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| 296 | }  | 
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| 297 |       if (isSubscribed.current) { | 
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| 298 |         dispatch({ | 
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| 299 | type: ActionTypes.UpdateFulfill,  | 
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| 300 | payload: value,  | 
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| 301 | meta,  | 
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| 302 | });  | 
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| 303 | }  | 
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| 304 | return value;  | 
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| 305 | },  | 
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| 306 | [endpoint, resolveEntityEndpoint, parseEntityResponse, handleError, addKey],  | 
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| 307 | );  | 
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| 308 | |||
| 309 | const deleteResource = useCallback(  | 
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| 310 |     async (entity: T): Promise<void> => { | 
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| 311 |       const meta = { key: keyFn(entity) }; | 
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| 312 |       dispatch({ | 
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| 313 | type: ActionTypes.DeleteStart,  | 
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| 314 | meta,  | 
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| 315 | });  | 
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| 316 |       try { | 
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| 317 | const response = await deleteRequest(  | 
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| 318 | resolveEntityEndpoint(endpoint, entity),  | 
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| 319 | );  | 
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| 320 |         if (!response.ok) { | 
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| 321 | throw new FetchError(response);  | 
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| 322 | }  | 
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| 323 |       } catch (error) { | 
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| 324 |         if (isSubscribed.current) { | 
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| 325 |           dispatch({ | 
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| 326 | type: ActionTypes.DeleteReject,  | 
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| 327 | payload: error,  | 
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| 328 | meta,  | 
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| 329 | });  | 
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| 330 | handleError(error);  | 
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| 331 | }  | 
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| 332 | throw error;  | 
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| 333 | }  | 
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| 334 |       if (isSubscribed.current) { | 
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| 335 |         dispatch({ | 
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| 336 | type: ActionTypes.DeleteFulfill,  | 
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| 337 | meta,  | 
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| 338 | });  | 
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| 339 | }  | 
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| 340 | },  | 
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| 341 | [endpoint, resolveEntityEndpoint, handleError, keyFn],  | 
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| 342 | );  | 
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| 343 | |||
| 344 | // Despite the usual guidelines, this should only be reconsidered if endpoint changes.  | 
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| 345 | // Changing doInitialRefresh after the first run (or refresh) should not cause this to rerun.  | 
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| 346 |   useEffect(() => { | 
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| 347 |     if (doInitialRefresh) { | 
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| 348 | refresh().catch(doNothing);  | 
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| 349 | }  | 
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| 350 | |||
| 351 | // Unsubscribe from promises when this hook is unmounted.  | 
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| 352 |     return (): void => { | 
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| 353 | isSubscribed.current = false;  | 
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| 354 | };  | 
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| 355 | |||
| 356 | // eslint-disable-next-line react-hooks/exhaustive-deps  | 
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| 357 | }, [endpoint]);  | 
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| 358 | |||
| 359 |   return { | 
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| 360 | values,  | 
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| 361 | initialRefreshFinished,  | 
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| 362 | indexStatus,  | 
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| 363 | createStatus,  | 
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| 364 | entityStatus,  | 
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| 365 | create,  | 
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| 366 | refresh,  | 
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| 367 | update,  | 
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| 368 | deleteResource,  | 
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| 369 | };  | 
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| 373 |