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<?php |
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namespace SilverStripe\MSSQL; |
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use DateTime; |
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use SilverStripe\ORM\Connect\Query; |
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/** |
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* A result-set from a MSSQL database. |
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*/ |
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class SQLServerQuery extends Query |
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{ |
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/** |
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* The SQLServerConnector object that created this result set. |
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* |
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* @var SQLServerConnector |
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*/ |
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private $connector; |
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/** |
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* The internal MSSQL handle that points to the result set. |
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* |
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* @var resource |
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*/ |
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private $handle; |
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/** |
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* Hook the result-set given into a Query class, suitable for use by sapphire. |
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* @param SQLServerConnector $connector The database object that created this query. |
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* @param resource $handle the internal mssql handle that is points to the resultset. |
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*/ |
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public function __construct(SQLServerConnector $connector, $handle) |
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{ |
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$this->connector = $connector; |
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$this->handle = $handle; |
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} |
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public function __destruct() |
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{ |
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if (is_resource($this->handle)) { |
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sqlsrv_free_stmt($this->handle); |
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} |
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} |
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public function getIterator() |
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{ |
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if (is_resource($this->handle)) { |
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while ($data = sqlsrv_fetch_array($this->handle, SQLSRV_FETCH_ASSOC)) { |
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// special case for sqlsrv - date values are DateTime coming out of the sqlsrv drivers, |
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// so we convert to the usual Y-m-d H:i:s value! |
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foreach ($data as $name => $value) { |
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if ($value instanceof DateTime) { |
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$data[$name] = $value->format('Y-m-d H:i:s'); |
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} |
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} |
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yield $data; |
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} |
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} |
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} |
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public function numRecords() |
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{ |
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if (!is_resource($this->handle)) { |
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return false; |
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} |
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// WARNING: This will only work if the cursor type is scrollable! |
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if (function_exists('sqlsrv_num_rows')) { |
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return sqlsrv_num_rows($this->handle); |
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} else { |
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user_error('MSSQLQuery::numRecords() not supported in this version of sqlsrv', E_USER_WARNING); |
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} |
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} |
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} |
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.