rfc:object-initializer
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rfc:object-initializer [2019/09/12 13:33] – Added bc brzuchal | rfc:object-initializer [2019/10/24 07:36] (current) – closing vote, moving to declined brzuchal | ||
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* Version: 1.0 | * Version: 1.0 | ||
* Date: 2019-09-03 | * Date: 2019-09-03 | ||
- | * Author: Michał Brzuchalski <michal.brzuchalski@gmail.com> | + | * Author: Michał Brzuchalski <brzuchal@php.net> |
- | * Status: | + | * Status: |
* First Published at: http:// | * First Published at: http:// | ||
- | |||
- | |||
===== Introduction ===== | ===== Introduction ===== | ||
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- Pass created a fully initialized object. | - Pass created a fully initialized object. | ||
- | That's where object initializer optimization can benefit with single expression statement and it can be used to initialize any kind of object // | + | In current PHP implementation with Typed Properties, it is possible to instantiate class which doesn' |
+ | properties in an uninitialized state. | ||
+ | |||
+ | That's where object initializer optimization can benefit with single expression statement and it can be used to initialize any kind of object // | ||
+ | required properties are properly initialized, | ||
+ | |||
+ | The initializer block can use any properties and variables available in the containing scope, but one has to be wary of the fact that initializers are run after constructors. | ||
===== Proposal ===== | ===== Proposal ===== | ||
Object initializers allow assigning values to any accessible properties of an object at creation time without having to invoke a constructor followed by lines of assignment statements. The object initializer syntax enables to specify arguments for a constructor or omit the arguments (and parentheses syntax). | Object initializers allow assigning values to any accessible properties of an object at creation time without having to invoke a constructor followed by lines of assignment statements. The object initializer syntax enables to specify arguments for a constructor or omit the arguments (and parentheses syntax). | ||
- | |||
- | The following example shows how to use an object initializer with a // | ||
<code php> | <code php> | ||
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} | } | ||
} | } | ||
- | |||
- | $customer = new Customer { | ||
- | id = 123, | ||
- | name = "John Doe", | ||
- | }; | ||
class Car | class Car | ||
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public string $vin; | public string $vin; | ||
} | } | ||
+ | </ | ||
+ | |||
+ | The following example shows how to use an object initializer with a '' | ||
+ | |||
+ | <code php> | ||
+ | <?php | ||
+ | |||
+ | $customer = new Customer { | ||
+ | id = 123, | ||
+ | name = "John Doe", | ||
+ | }; | ||
$car = new Car { | $car = new Car { | ||
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</ | </ | ||
- | The object initializers syntax allows to create an instance, and after that, it assigns the newly created | + | > **Note!** If in current scope there are constants with exactly the same name as property names used in the above example, they do not impact |
- | Above example is an equivalent to the previous one. | + | The following |
<code php> | <code php> | ||
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The main difference is that object initializers allow creating a new object, with its assigned properties in a single expression. For eg. factory methods where normally a significant amount of argument has default values or simple Data Transfer Objects could benefit. | The main difference is that object initializers allow creating a new object, with its assigned properties in a single expression. For eg. factory methods where normally a significant amount of argument has default values or simple Data Transfer Objects could benefit. | ||
- | > Note! Currently, language allows instantiating object and initializing only a subset of typed non-nullable properties without a default value. These rules apply to object initializer the same way, meaning the creation of properly initialized object state is in authors responsibility, | + | > **Note!** Currently, language allows instantiating object and initializing only a subset of typed non-nullable properties without a default value. These rules apply to object initializer the same way, meaning the creation of properly initialized object state is in authors responsibility, |
- | ==== Constructors | + | ==== Restrictions |
+ | Using Object Initializer enforce that if a class is instantiated with the Object Initializer, | ||
+ | This helps to avoid bugs where a property is added to the class but forgot to be assigned it a value in all cases where the class is instantiated and initialized. | ||
- | Due to the fact that initializer block purpose is a simplification of instantiating and initializing object properties, constructors are called before initialization takes apart. Constructors allow initializing default values // | + | The object initializers syntax allows to create an instance, and after that, it assigns the newly created object, with its assigned properties, to the variable in the assignment. |
+ | |||
+ | <code php> | ||
+ | <?php | ||
+ | |||
+ | $customer = new Customer { | ||
+ | name = "John Doe", | ||
+ | }; // throws RuntimeException: | ||
+ | |||
+ | $car = new Car { | ||
+ | yearOfProduction = 2019, | ||
+ | }; // throws RuntimeException: | ||
+ | </ | ||
+ | |||
+ | |||
+ | ==== Constructors ==== | ||
+ | Due to the fact that initializer block purpose is a simplification of instantiating and initializing object properties, constructors are called before initialization takes apart. Constructors allow initializing default values // | ||
Due to the fact that objects in PHP simply have constructor directly declared in class definition or indirectly through the defaulting constructor, | Due to the fact that objects in PHP simply have constructor directly declared in class definition or indirectly through the defaulting constructor, | ||
+ | |||
+ | > **Note!** Object instantiation allows only constructors without required arguments to be used. Any class which requires passing arguments to constructor cannot be used in combination with object initializer. | ||
+ | |||
<code php> | <code php> | ||
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- | > Note! Classes without constructor desired to mimick " | + | > **Note!** Classes without constructor desired to mimick " |
- | > Note! If a class needs validation upon to validate its invariants a proper validation logic needs to be called after initialization. To combine it with object initializer and keep the validation process encapsulated, | + | > **Note!** If a class needs validation upon to validate its invariants a proper validation logic needs to be called after initialization. To combine it with object initializer and keep the validation process encapsulated, |
==== Lexical scope ==== | ==== Lexical scope ==== | ||
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Initializer block allows assigning values to properties accessible from the current class context. This means if used to initialize object properties from inside the same class like for eg. using named static constructor all standard visibility rules apply as it is just a simplification of object creation and assigning values statements. | Initializer block allows assigning values to properties accessible from the current class context. This means if used to initialize object properties from inside the same class like for eg. using named static constructor all standard visibility rules apply as it is just a simplification of object creation and assigning values statements. | ||
- | Above example shows the correct behaviour of visibility rules. | + | The following |
<code php> | <code php> | ||
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Initializer block stands instead of constructor arguments which means in case of anonymous classes that place is right before the class definition. | Initializer block stands instead of constructor arguments which means in case of anonymous classes that place is right before the class definition. | ||
- | Above example shows how to use object initializer with anonymous classes. | + | The following |
<code php> | <code php> | ||
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Dynamic properties can be set by their name or by a variable which holds the name of property. | Dynamic properties can be set by their name or by a variable which holds the name of property. | ||
- | Above example shows how to use object initializer with dynamic properties. | + | The following |
<code php> | <code php> | ||
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}; | }; | ||
</ | </ | ||
- | |||
- | |||
===== Backward Incompatible Changes ===== | ===== Backward Incompatible Changes ===== | ||
- | This proposal changes the meaning of above example which uses curly brace to fetch array offset //(which is already deprecated since PHP 7.4)// which is very rare usage. | + | This proposal changes the meaning of the above example which uses a curly brace to fetch array offset //(which is already deprecated since PHP 7.4)// which is very rare usage. |
<code php> | <code php> | ||
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$foo = [123 => Foo:: | $foo = [123 => Foo:: | ||
new $foo { | new $foo { | ||
- | $var =123 | + | $var = 123 |
}; | }; | ||
+ | </ | ||
+ | |||
+ | ===== Reflection ===== | ||
+ | Both '' | ||
+ | |||
+ | <code php> | ||
+ | <?php | ||
+ | |||
+ | $reflectionClass = new ReflectionClass(Customer:: | ||
+ | $customer = $reflectionClass-> | ||
+ | // equivalent to | ||
+ | $customer = new Customer {name = ' | ||
</ | </ | ||
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As this is a language change, a 2/3 majority is required. | As this is a language change, a 2/3 majority is required. | ||
- | The vote is a straight Yes/No vote for accepting the RFC and merging the patch. | + | The vote is a straight Yes/No vote for accepting the RFC. |
+ | |||
+ | <doodle title=" | ||
+ | * Yes | ||
+ | * No | ||
+ | </ | ||
+ | . | ||
+ | <doodle title=" | ||
+ | * = | ||
+ | * => | ||
+ | </ | ||
===== Patches and Tests ===== | ===== Patches and Tests ===== |
rfc/object-initializer.1568295195.txt.gz · Last modified: 2019/09/12 13:33 by brzuchal