Traits is a code reuse mechanism prepared for single inheritance languages like PHP. Traits are designed to reduce the constraints of single-inheritance languages and allow developers to freely reuse method sets in independent classes within different hierarchies.
Since PHP 5.4.0, PHP implements a method of code reuse called traits.
Traits is a code reuse mechanism prepared for single inheritance languages like PHP. Traits are designed to reduce the constraints of single-inheritance languages and allow developers to freely reuse method sets in independent classes within different hierarchies. The semantics of traits and class composition define a way to reduce complexity and avoid the typical problems associated with traditional multiple inheritance and mixins.
Trait is similar to a class, but is only designed to combine functionality in a fine-grained and consistent way. Trait cannot be instantiated by itself. It adds a combination of horizontal features to traditional inheritance; that is, members of application classes do not need to be inherited.
Trait was added in PHP5.4. It is neither an interface nor a class. Mainly to solve the limitations of single inheritance languages. It is a solution to multiple inheritance in PHP. For example, it would be very troublesome to inherit two Abstract Classes at the same time. Trait is designed to solve this problem. It can be added to one or more existing classes. It declares what the class can do (indicating its interface characteristics), and also contains the specific implementation (indicating its class characteristics)
Simple use
First, Of course, declare a trait. PHP5.4 adds the trait keyword
?
| ##1234
|
trait first_trait {
function first_method() { }
function second_method() { }
}
|
At the same time, if you want to use the Trait in Class, use the use keyword
?
| ## 12345678
|
class first_class {
use first_trait;
}
$obj = new first_class();
$obj->first_method();
$obj->second_method();
|
Use multiple Traits
You can use multiple Traits in the same Class
?
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
|
trait first_trait
{
function first_method() { echo "method"; }
}
trait second_trait {
function second_method() { echo "method"; }
}
class first_class {
use first_trait, second_trait;
}
$obj= new first_class();
$obj->first_method();
$obj->second_method();
|
Nesting between Traits
At the same time, Traits can also be nested within each other, such as
?
|
1
2
3
4
5 6
7
8
9
10
11
12
13
14
15
16
|
trait first_trait {
function first_method() { echo "method"; }
}
trait second_trait {
use first_trait;
function second_method() { echo "method"; }
}
class first_class {
use second_trait;
}
$obj= new first_class();
$obj->first_method();
$obj->second_method();
|
Abstract Method of Trait
We can declare the abstract method that needs to be implemented in Trait, so that the Class that uses it must implement it
?
| ##123 45678910
11
|
##trait first_trait {
function first_method() { "method"
// You can add modifiers here to indicate the call Classes must implement it
abstract public function second_method();
}
class first_method {
use first_trait;
function second_method() {
}
}
|
Trait conflict
Using multiple Traits at the same time will inevitably lead to conflicts, which we need to resolve. PHP5.4 brings related keyword syntax from the aspect of grammar: insteadof and as. For usage, see
?
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
|
trait first_trait {
function first_function() {
echo "From First Trait";
}
}
##trait second_trait {
// The name here is the same as first_trait, there will be a conflict
function first_function() {
echo "From Second Trait";
}
}
class first_class {
use first_trait, second_trait {
##first_trait::first_function instead of second_trait;
} ## declared in second_trait #} <p class="line number19 index18 alt2" style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;vertical-align:baseline;min-height:auto;white-space:pre;"><code class="php variable" style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:rgb(170,119,0);">$obj = new first_class();
$obj->first_function();
|
The above are some basic uses of Traits. For more details, please refer to the official manual. Here are some points to note:
Trait will override the parent class method inherited by the calling class
Trait cannot be instantiated using new like Class
A single Trait can be composed of multiple Traits
In a single Class, multiple Traits can be used
Trait supports modifiers, For example, final, static, abstract
We can use insteadof and as operators to resolve conflicts between Traits
Related recommendations:
About Trait in Detailed explanation and application in php
About Trait issues in PHP
Detailed explanation on the use of traits reuse mechanism in php
The above is the detailed content of Sharing the characteristics and functions of Trait in PHP. For more information, please follow other related articles on the PHP Chinese website!
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
