dongzhengzhong1282 2014-02-08 11:07
浏览 63
已采纳

PHP闭包作为静态类变量

I wanted to have a static closure variable in my class, so that people can change the behavior of a specific part of the code. However, I can't seem to be able to initialize it anywhere.

First I tried this:

public static $logger = function($sql) { print_r($sql); };

But apparently PHP can't handle that. Ok, so I made a static init method:

public static $logger;

static function init() {
    /* if (!Base::logger) */
    Base::logger = function($sql) { print_r($sql); };
}

And call it at the end of the file, outside class definition. But this also give me a syntax error: Parse error: syntax error, unexpected '=' in [file] on line [line]. Any hints?

  • 写回答

1条回答 默认 最新

  • douyong1886 2014-02-08 11:11
    关注

    The syntax error is right where the error message tells you it is (it would have been even easier to spot if you had given us line numbers...): a missing $-sign.

    Base::$logger = function (...)
    

    In addition to that, you migth want to use self:: instead of Base::, this ensure the code will work without any additional changes if you ever rename the class

    self::$logger = function (...)
    

    You can improve this code even further, when changing the initializer to a getter that JIT-creates the closure:

    private static $logger = NULL;
    
    public static function getLogger () {
        if (self::$logger === NULL) {
            self::$logger = function ($sql) {print_r($sql);};
        }
        return self::$logger;
    }
    

    [Edit] Based on your comment on this: the clean OOP way of being able to change $logger would be to use a setter:

    public static function setLogger ($closure) {
        self::$logger = $closure;
    }
    

    COmbining this and the getter from above ensures that you always get the value set by the setter, and, if none has been set yet, the default value. Using the setter to set the value back to NULL makes the getter create the default again, which is anoth er plus.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

报告相同问题?

悬赏问题

  • ¥15 关于c++外部库文件宏的问题,求解
  • ¥15 office打开卡退(新电脑重装office系统后)
  • ¥300 FLUENT 火箭发动机燃烧EDC仿真
  • ¥15 【Hadoop 问题】Hadoop编译所遇问题hadoop-common: make failed with error code 2
  • ¥15 vb6.0+webbrowser无法加载某个网页求解
  • ¥15 RPA财务机器人采购付款流程
  • ¥15 计算机图形多边形及三次样条曲线绘制
  • ¥15 根据protues画的图用keil写程序
  • ¥200 如何使用postGis实现最短领规划?
  • ¥15 pyinstaller打包错误