Example explanation of simple factory pattern in PHP

An example explanation of the simple factory pattern in PHP. You can refer to it briefly.

Simple factory pattern:
①Abstract base class: Define some abstract methods in the class to implement in subclasses
②Subclasses that inherit from abstract base classes: Implement abstract methods in the base class
③Factory class: used to instantiate objects

After reading the article, look back at this picture, the effect will be better

Use encapsulation Way

代码如下

复制代码

class Calc{
/**
* 计算结果
*
* @param int|float $num1
* @param int|float $num2
* @param string $operator
* @return int|float
*/
public function calculate($num1,$num2,$operator){
try {
$result=0;
switch ($operator){
case '+':
$result= $num1+$num2;
break;
case '-':
$result= $num1-$num2;
break;
case '*':
$result= $num1*$num2;
break;
case '/':
if ($num2==0) {
throw new Exception("除数不能为0");
}
$result= $num1/$num2;
break;
return $result;
}
}catch (Exception $e){
echo "您输入有误:".$e->getMessage();
            }
        }
    }
    $test=new Calc();
//    echo $test->calculate(2,3,'+');//打印:5
    echo $test->calculate(5,0,'/');//打印:您输入有误:除数不能为0
?>

Advantages: The above code uses object-oriented encapsulation features. As long as the include class is included, other pages can use it at will

Disadvantages: It cannot be flexibly expanded and maintained
For example: want To add a "remainder" operation, you need to add a branch statement in the switch statement block. The code needs to be changed as follows
Add branch statement

The code is as follows	Copy code

代码如下	复制代码
class Calc{ public function calculate($num1,$num2,$operator){ try { $result=0; switch ($operator){ //......省略...... case '%': $result= $num1%$num2; break; //......省略...... } }catch (Exception $e){ echo "您输入有误:".$e->getMessage(); } } } ?>

class Calc{ public function calculate($num1,$num2,$operator){ try { $result=0; switch ($operator){ //......Omitted. . .... case '%': $result= $num1%$num2; break; //...Omit... } ; ?> ;

Code analysis: Using the above method to add new functional operations to the calculator has the following disadvantages

① It is necessary to modify the original code block, which may be modified in order to "add new functions" When I have the code, I accidentally correct the original code to the wrong one
② If there are many functions to be added, such as: 'power', 'square root', 'logarithm', 'trigonometric function', 'statistics' ', or add some programmer-specific calculation functions, such as: And, Or, Not, Xor, so you need to add N branch statements to the switch statement. Imagine that if a calculation function has twenty or thirty case branch statements, the code will exceed one screen. Not only will the readability of the code be greatly reduced, but the key is that in order to add small functions, other unrelated functions must be involved. Explanation, this greatly reduces the execution efficiency of the program
Solution: Adopt OOP inheritance and polymorphic ideas
Initial implementation of simple factory pattern

The code is as follows	Copy code

代码如下	复制代码
/** * 操作类 * 因为包含有抽象方法，所以类必须声明为抽象类 / abstract class Operation{ //抽象方法不能包含函数体 abstract public function getValue($num1,$num2);//强烈要求子类必须实现该功能函数 } /* * 加法类 / class OperationAdd extends Operation { public function getValue($num1,$num2){ return $num1+$num2; } } /* * 减法类 / class OperationSub extends Operation { public function getValue($num1,$num2){ return $num1-$num2; } } /* * 乘法类 / class OperationMul extends Operation { public function getValue($num1,$num2){ return $num1$num2; } } /** * 除法类 */ class OperationDiv extends Operation { public function getValue($num1,$num2){ try { if ($num2==0){ throw new Exception("除数不能为0"); }else { return $num1/$num2; } }catch (Exception $e){ echo "错误信息：".$e->getMessage(); } } } ?>

/** * Operation class * Because it contains abstract methods, the class must be declared as an abstract class */ abstract class Operation{ //Abstract methods cannot contain function bodies abstract public function getValue($num1,$num2);//It is strongly required that subclasses must implement this Function function } /** * Addition class */ class OperationAdd extends Operation { public function getValue($num1,$num2){ return $num1+$num2; } } /** * Subtraction class*/ class OperationSub extends Operation { public function getValue($num1,$num2){ return $num1-$num2; } } /** * Multiplication class*/ class OperationMul extends Operation { public function getValue($num1,$num2){ return $num1*$num2; } } /** * Division class*/ class OperationDiv extends Operation { public function getValue($num1,$num2){ try { if " } $e){ echo "Error message: ".$e->getMessage(); . /table>

adopts the object-oriented inheritance feature. First declare a virtual base class, and specify the method that the subclass must implement in the base class (getValue())

Analysis: By adopting the object-oriented inheritance feature , we can easily extend the original program, such as: 'power', 'square root', 'logarithm', 'trigonometric function', 'statistics' and so on.

Find the remainder

The code is as follows

代码如下	复制代码
/** * 求余类（remainder） * */ class OperationRem extends Operation { public function getValue($num1,$num2){ return $num1%$num12; } } ?>

Copy code

/**
* Find remainder (remainder)

class OperationRem extends Operation {

代码如下

复制代码

/**
* 工程类，主要用来创建对象
* 功能：根据输入的运算符号，工厂就能实例化出合适的对象
*
*/
class Factory{
public static function createObj($operate){
switch ($operate){
case '+':
return new OperationAdd();
break;
case '-':
return new OperationSub();
break;
case '*':
return new OperationSub();
break;
case '/':
return new OperationDiv();
break;
}
}
}
$test=Factory::createObj('/');
$result=$test->getValue(23,0);
echo $result;
?>

public function getValue($num1,$ num2){ return $num1%$num12; This class inherits the virtual base class), completes the corresponding functions in the class (for example: the calculation of exponentiation), and greatly reduces the degree of coupling, which facilitates future maintenance and expansionNow there is another question The unresolved problem is how to let the program instantiate the corresponding object according to the operator input by the user? Solution: Use a separate class to implement the instantiation process. This class is the factoryThe code is as follows:Factory class

The code is as follows

Copy code

/**<🎜> * Engineering class, mainly used to create objects <🎜> * Function: According to the input operation symbols, the factory can instantiate the appropriate object <🎜> *<🎜>*/<🎜> class Factory{<🎜> public static function createObj($operate){<🎜> switch ($operate){<🎜> case '+':<🎜> return new OperationAdd( ). ;<🎜> case '/':<🎜> return new OperationDiv(); 🎜> }<🎜> $test=Factory::createObj('/') ;<🎜> $result=$test->getValue(23,0); echo $result;?>

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