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                <?php  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @copyright Copyright (C) eZ Systems AS. All rights reserved.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 * @license For full copyright and license information view LICENSE file distributed with this source code.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                namespace eZ\Publish\Core\REST\Server\Tests\Input\Parser\SortClause;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\API\Repository\Values\Content\Query;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\API\Repository\Values\Content\Query\SortClause\Field;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\Core\REST\Server\Input\Parser\SortClause\Field as FieldParser;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use eZ\Publish\Core\REST\Server\Tests\Input\Parser\BaseTest;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                class FieldTest extends BaseTest  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Tests the Field parser.  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                     */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    public function testParse()  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    { | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $inputArray = [  | 
            
            
                                                                        
                            
            
                                    
            
            
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                            'Field' => [  | 
            
            
                                                                        
                            
            
                                    
            
            
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                                'identifier' => 'content/field',  | 
            
            
                                                                        
                            
            
                                    
            
            
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                                'direction' => Query::SORT_ASC,  | 
            
            
                                                                        
                            
            
                                    
            
            
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                            ],  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        ];  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $fieldParser = $this->getParser();  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $result = $fieldParser->parse($inputArray, $this->getParsingDispatcherMock());  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        $this->assertEquals(  | 
            
            
                                                                        
                            
            
                                    
            
            
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                            new Field('content', 'field', Query::SORT_ASC), | 
            
            
                                                                        
                            
            
                                    
            
            
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                            $result,  | 
            
            
                                                                        
                            
            
                                    
            
            
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                            'Field parser not created correctly.'  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        );  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Test Field parser throwing exception on missing sort clause.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @expectedException \eZ\Publish\Core\REST\Common\Exceptions\Parser  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @expectedExceptionMessage The <Field> sort clause doesn't exist in the input structure  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function testParseExceptionOnMissingSortClause()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $inputArray = [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'name' => 'Keep on mocking in the free world',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        ];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $fieldParser = $this->getParser();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $fieldParser->parse($inputArray, $this->getParsingDispatcherMock());  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Test Field parser throwing exception on invalid direction format.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @expectedException \eZ\Publish\Core\REST\Common\Exceptions\Parser  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @expectedExceptionMessage Invalid direction format in <Field> sort clause  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                                                    
                                                                                                        
            
            
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                View Code Duplication | 
                    public function testParseExceptionOnInvalidDirectionFormat()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $inputArray = [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'Field' => [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                'identifier' => 'content/field',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                'direction' => 'mock',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            ],  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        ];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $fieldParser = $this->getParser();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $fieldParser->parse($inputArray, $this->getParsingDispatcherMock());  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Returns the Field parser.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return \eZ\Publish\Core\REST\Server\Input\Parser\SortClause\Field  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected function internalGetParser()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return new FieldParser();  | 
            
                            
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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_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.