The drawback of the above code is that you would have to call `trim()` everywhere in your code where you might set the `label`
The drawback of the above code is that you would have to call `trim()` everywhere in your code where you might set the `label`
property. If, in the future, the `label` property gets a new requirement, such as the first letter must be captialized, you would again have to modify every bit of code that assigns a value to `label`. The repetition of code leads to bugs, and is a practice you want to avoid as much as possible.
property. If, in the future, the `label` property gets a new requirement, such as the first letter must be capitalized, you would again have to modify every bit of code that assigns a value to `label`. The repetition of code leads to bugs, and is a practice you want to avoid as much as possible.
To solve this problem, Yii introduces a base class called [[yii\base\Object]] that supports defining properties
To solve this problem, Yii introduces a base class called [[yii\base\Object]] that supports defining properties
based on *getter* and *setter* class methods. If a class needs that functionality, it should extend from
based on *getter* and *setter* class methods. If a class needs that functionality, it should extend from
@ -28,7 +28,7 @@ namespace app\components;
use yii\base\Object;
use yii\base\Object;
class Foo extend Object
class Foo extends Object
{
{
private $_label;
private $_label;
@ -44,10 +44,10 @@ class Foo extend Object
}
}
```
```
(To be clear, the getter and setter methods create the property `label`, which in this case internally refer to a private attributed named `_label`.)
(To be clear, the getter and setter methods create the property `label`, which in this case internally refers to a private attribute named `_label`.)
Properties defined by getters and setters can be used like class member variables. The main difference is that
Properties defined by getters and setters can be used like class member variables. The main difference is that
when such a property is being read, the corresponding getter method will be called; when the property is
when such property is being read, the corresponding getter method will be called; when the property is
being assigned a value, the corresponding setter method will be called. For example:
being assigned a value, the corresponding setter method will be called. For example:
```php
```php
@ -58,20 +58,20 @@ $label = $object->label;
$object->label = 'abc';
$object->label = 'abc';
```
```
A property defined by a getter without a setter is *read only*. Trying to assign a value to such a property will cause
A property defined by a getter without a setter is *read only*. Trying to assign a value to such property will cause
an [[yii\base\InvalidCallException|InvalidCallException]]. Similarly, a property defined by a setter without a getter
an [[yii\base\InvalidCallException|InvalidCallException]]. Similarly, a property defined by a setter without a getter
is *write only*, and trying to read such a property will also cause an exception. It is not common to have write-only
is *write only*, and trying to read such property will also cause an exception. It is not common to have write-only
properties.
properties.
There are several special rules for, and limitations on, the properties defined via getters and setters:
There are several special rules for, and limitations on, the properties defined via getters and setters:
* The names of such properties are *case-insensitive*. For example, `$object->label` and `$object->Label` are the same.
* The names of such properties are *case-insensitive*. For example, `$object->label` and `$object->Label` are the same.
This is because method names in PHP are case-insensitive.
This is because method names in PHP are case-insensitive.
* If the name of such a property is the same as a class member variable, the latter will take precedence.
* If the name of such property is the same as a class member variable, the latter will take precedence.
For example, if the above `Foo` class has a member variable `label`, then the assignment `$object->label = 'abc'`
For example, if the above `Foo` class has a member variable `label`, then the assignment `$object->label = 'abc'`
will affect the *member variable* 'label'; that line would not call the `setLabel()` setter method.
will affect the *member variable* 'label'; that line would not call the `setLabel()` setter method.
* These properties do not support visibility. It makes no difference for the visibility of a property
* These properties do not support visibility. It makes no difference for the visibility of a property
if the defining getter or setter method is public, protected or private.
if the defining getter or setter method is public, protected or private.
* The properties can only be defined by *non-static* getters and/or setters. Static methods will not be treated in this same manner.
* The properties can only be defined by *non-static* getters and/or setters. Static methods will not be treated in the same manner.
Returning back to the problem described at the beginning of this guide, instead of calling `trim()` everywhere a `label` value is assigned, `trim()` now only needs to be invoked within the setter `setLabel()`. And if a new requirement comes that requires the label be initially capitalized, the `setLabel()` method can quickly be modified without touching any other code. The one change will universally affect every assignment to `label`.
Returning back to the problem described at the beginning of this guide, instead of calling `trim()` everywhere a `label` value is assigned, `trim()` now only needs to be invoked within the setter `setLabel()`. And if a new requirement comes that requires the label to be initially capitalized, the `setLabel()` method can quickly be modified without touching any other code. The one change will universally affect every assignment to `label`.
Alexander Makarov
10 years ago