php - 如何创建带有可选参数的构造函数？

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我有 __construct($parameter)

public function __construct($nick) {
    $query = "SELECT * FROM Users WHERE nick='".$nick."'";
    $result = App::runQuery($query);
    $user = $result->fetch_object();

    $this->id = $user->id;
    $this->nick = $user->nick;
    $this->email = $user->email;
    $this->password = $user->password;
    $this->birthDay = $user->birthDay;
    $this->sex = $user->sex;
    $this->about = $user->about;
    $this->city = $user->city;
    $this->photo = $user->photo;
    $this->following = $user->following;
    $this->followers = $user->followers;
    $this->statu = $user->statu; 

}

现在我想要一个没有参数的默认构造函数，如下所示:

public function __construct() {

    $this->id = NULL;
    $this->nick = NULL;
    $this->email = NULL;
    $this->password = NULL;
    $this->birthDay = NULL;
    $this->sex = NULL;
    $this->about = NULL;
    $this->city = NULL;
    $this->photo = NULL;
    $this->following = NULL;
    $this->followers = NULL;
    $this->statu = NULL; 

}

但是出了点问题，我得到这样的错误:

Fatal error: Cannot redeclare User::__construct() in /Applications/MAMP/htdocs/xxx/Application/User.php on line 33

如何同时拥有两个带参数和不带参数的构造函数？

最佳答案

PHP 中没有重载；你不能有名称相同但参数不同的方法

由于您的所有属性都将默认为 null，因此您没有理由自己动手做。我建议执行以下操作:

public function __construct($nick = null) {
    if ($nick != null) {
        $query = "SELECT * FROM Users WHERE nick='".$nick."'";
        $result = App::runQuery($query);
        $user = $result->fetch_object();

        $this->id = $user->id;
        $this->nick = $user->nick;
        $this->email = $user->email;
        $this->password = $user->password;
        $this->birthDay = $user->birthDay;
        $this->sex = $user->sex;
        $this->about = $user->about;
        $this->city = $user->city;
        $this->photo = $user->photo;
        $this->following = $user->following;
        $this->followers = $user->followers;
        $this->statu = $user->statu; 
    }
}

上述代码的替代方法是拥有多个静态构造函数方法，并使用私有(private)构造函数:

private function __construct() {
}

public static function createFromNick($nick) {
    $self = new self();

    $query = "SELECT * FROM Users WHERE nick='".$nick."'";
    $result = App::runQuery($query);
    $user = $result->fetch_object();

    $self->id = $user->id;
    $self->nick = $user->nick;
    $self->email = $user->email;
    $self->password = $user->password;
    $self->birthDay = $user->birthDay;
    $self->sex = $user->sex;
    $self->about = $user->about;
    $self->city = $user->city;
    $self->photo = $user->photo;
    $self->following = $user->following;
    $self->followers = $user->followers;
    $self->statu = $user->statu;

    return $self;
}

public static function createEmpty() {
    return new self();
}

关于php - 如何创建带有可选参数的构造函数？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28395855/

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