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Detailed explanation of example code of PHP Inversion of Control (IOC) and Dependency Injection (DI)
Detailed explanation of example code of PHP Inversion of Control (IOC) and Dependency Injection (DI)
Let’s look at an example first:
<?php
class A
{
public $b;
public $c;
public function A()
{
//TODO
}
public function Method()
{
$this->b=new B();
$this->c=new C();
$this->b->Method();
$this->c->Method();
//TODO
}
}
class B
{
public function B()
{
//TODO
}
public function Method()
{
//TODO
echo 'b';
}
}
class C
{
public function C()
{
//TODO
}
public function Method()
{
//TODO
echo 'c';
}
}
$a=new A();
$a->Method();
?>The above code, we can easily understand one sentence:
A classDepend on Class B and Class C
In other words, if in the future development process, Class B or Class C needs to be modified, once thefunction is renamed, the function If the number of parameters changes, or even if the entire class structure is adjusted, we must also make corresponding adjustments to Class A. The independence of Class A is lost, which is very inconvenient during the development process, which is what we call "One thing affects the whole body." If the two categories are written by two people separately, conflicts often arise at this time. . .
If we really need to change categories B and C, is there any way to not change the code of category A or to change it as little as possible? Inversion of control is used here.High-level modules should not depend on low-level modules, both should rely on abstractions.Inversion of Control (IOC) is an idea,
Dependency Injection (DI) is a method to implement this idea.
The first method is called: constructor injection (this method is not recommended, but it is better than not using it)class A
{
public $b;
public $c;
public function A($b,$c)
{
$this->b=$b;
$this->c=$c;
}
public function Method()
{
$this->b->Method();
$this->c->Method();
}
}$a=new A(new B(),new C()); $a->Method();
class B
{
public function B()
{
//TODO
}
public function Method()
{
//TODO
echo 'b';
}
}
class B1 extends B
{
public function B1()
{
//TODO
}
public function Method()
{
echo 'b1';
}
}
class B2 extends B
{
public function B2()
{
//TODO
}
public function Method()
{
echo 'b2';
}
}$a=new A(new B2(),new C()); $a->Method();
Factory modeInjection (recommended)
class Factory
{
public function Factory()
{
//TODO
}
public function create($s)
{
switch($s)
{
case 'B':
{
return new B();
break;
}
case 'C':
{
return new C();
break;
}
default:
{
return null;
break;
}
}
}
}class A
{
public $b;
public $c;
public function A()
{
//TODO
}
public function Method()
{
$f=new Factory();
$this->b=$f->create('B');
$this->c=$f->create('C');
$this->b->Method();
$this->c->Method();
//TODO
}
}constructor of classes B and C changes, such as modifying function parameters, etc., we Just change the Factory class.
Abstraction should not depend on details, details should depend on abstraction.Abstract the methods in classes B and C and make an
interface IMethod
{
public function Method();
}variables and $c variables in the class are no longer a specific variable, but an abstract class type variable. Until the moment of running, their identity is unknown. How is the Method method implemented?
class B implements IMethod
{
public function B()
{
//TODO
}
public function Method()
{
//TODO
echo 'b';
}
}
class C implements IMethod
{
public function C()
{
//TODO
}
public function Method()
{
//TODO
echo 'c';
}
}The above is the detailed content of Detailed explanation of example code of PHP Inversion of Control (IOC) and Dependency Injection (DI). For more information, please follow other related articles on the PHP Chinese website!
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