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Home php教程 php手冊(cè) php中關(guān)于抽象(abstract)類(lèi)和抽象方法的問(wèn)題解析

php中關(guān)于抽象(abstract)類(lèi)和抽象方法的問(wèn)題解析

Jun 13, 2016 am 09:46 AM
abstract php one under about us abstract method of parse question

下面我們一起來(lái)看看php中關(guān)于抽象(abstract)類(lèi)和抽象方法的問(wèn)題解析,希望本文章對(duì)各位同學(xué)會(huì)有所幫助哦。

在面向?qū)ο螅∣OP)語(yǔ)言中,一個(gè)類(lèi)可以有一個(gè)或多個(gè)子類(lèi),而每個(gè)類(lèi)都有至少一個(gè)公有方法作為外部代碼訪問(wèn)的接口。而抽象方法就是為了方便繼承而引入的,現(xiàn)在來(lái)看一下抽象類(lèi)和抽象方法分別是如何定義以及他們的特點(diǎn)。

什么是抽象方法?我們?cè)陬?lèi)里面定義的只有方法名沒(méi)有方法體的方法就是抽象方法,所謂沒(méi)有方法體就是在方法聲明的時(shí)候沒(méi)有大括號(hào)以及其中的內(nèi)容,而是直接聲明時(shí)在方法名后加上分號(hào)結(jié)束,另外在聲明抽象方法時(shí)還要加一個(gè)關(guān)鍵字"abstract"來(lái)修飾。


1、抽象關(guān)鍵字 :abstract

抽象就是無(wú)法確切的說(shuō)明,但又有一定的概念或者名稱(chēng),在PHP中聲明一個(gè)抽象類(lèi)或者方法我們需要使用adstract關(guān)鍵字。

2、抽象方法和抽象類(lèi)的定義

一個(gè)類(lèi)中至少有一個(gè)方法是抽象的,我們稱(chēng)之為抽象類(lèi)。所以如果定義抽象類(lèi)首先定義抽象方法。

abstract class class1{?????????????????????????????????????????????

?? abstract function fun1();
……
}

1、類(lèi)中至少有一個(gè)抽象方法
2、抽象方法不允許有{ }
3、抽象方法前面必須要加abstract


3、抽象類(lèi)和方法使用規(guī)則


抽象類(lèi)的幾個(gè)特點(diǎn):

1、不能被實(shí)例化,只能被繼承

2、繼承的派生類(lèi)當(dāng)中要把所有抽象方法重載才能實(shí)例化

關(guān)于抽象方法的聲明如下:

?代碼如下 復(fù)制代碼

abstract function fun1();

?>


什么是抽象類(lèi)呢?只要一個(gè)類(lèi)里面有一個(gè)方法是抽象方法,那么這個(gè)類(lèi)就必須定義為抽象類(lèi)。抽象類(lèi)也要使用關(guān)鍵字"abstract"來(lái)修飾,抽象類(lèi)不能實(shí)例化對(duì)象,所以抽象方法作為子類(lèi)方法重載的模板使用的,且要把繼承的抽象類(lèi)里的方法都實(shí)現(xiàn)。

關(guān)于抽象類(lèi)以及抽象類(lèi)的實(shí)現(xiàn)舉例如下:

?代碼如下 復(fù)制代碼

abstract class User{? //定義抽象類(lèi)
??? abstract protected function getUser(); //定義抽象方法
??? public function print_content(){
??????? print $this->getUser();
??? }
}

class vipUser extends User{
??? protected function getUser(){
??????? return "抽象類(lèi)與抽象方法";
??? }
}

$user=new vipUser(); //實(shí)例化子類(lèi)
$user->print_content(); //抽象類(lèi)與抽象方法
?>


注意:抽象類(lèi)繼承另外一個(gè)抽象類(lèi)時(shí)(目的是對(duì)該抽象類(lèi)的擴(kuò)展),不能重寫(xiě)父類(lèi)的抽象方法。

在PHP5.1中,抽象類(lèi)中支持靜態(tài)抽象方法。下面這個(gè)例子,看到靜態(tài)抽象方法可以聲明。實(shí)現(xiàn)這個(gè)方法時(shí),必須是靜態(tài)的方法。

?代碼如下 復(fù)制代碼

abstract class User{
?protected static? $sal=0;
?static abstract function getSal();
?static abstract function setSal($sal);
}
class VipUser extends User{
?static function getSal(){
??return self::$sal;
?}
?static function setSal($sal){
??self::$sal=$sal;
?}
}
VipUser::setSal(100);
echo "you sal is " . VipUser::getSal();
?>

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