var self =这在Coffeescript中

Question

我在使用Coffeescript时处理一些范围问题.

drawFirstLine: (currentAngle)  ->
    currentAngle = currentAngle # = 1

    switch @type
        # set @endAngle to pick up later on
        # Math.PI * 2 is the endpoint of a circle divided by seconds times current seconds
        when "seconds" then @endAngle = Math.PI * 2 / 60 * @seconds
        when "minutes" then @endAngle = Math.PI * 2 / 60 * @minutes
        when "hours" then @endAngle = Math.PI * 2 / 24 * @hours


    @context.arc(@center_x, @center_y, 100, @startAngle, currentAngle, @counterClockWise)
    @context.lineWidth = 15

    console.log('drawn')

    text = "28px sans-serif";
    @context.fillText(text, @center_x - 28, @center_y - @canvas.width / 5)

    @context.stroke()


    currentAngle++;
    if currentAngle < @endAngle
        requestAnimationFrame( -> @drawFirstLine(currentAngle / 100) )

正如您在上面的代码底部所看到的,我试图一次又一次地调用我们所在的函数.但问题是我不能@drawFirstLine在另一个函数内部使用(requestAnimationFrame函数).在简单的JavaScript中我可以使用var self = this并引用自我.但是有人知道如何在coffeescript中处理这个问题吗？

提前致谢,

Answer 1

使用胖箭头.

requestAnimationFrame( => @drawFirstLine(currentAngle / 100) )

编译为:

var _this = this;

requestAnimationFrame(function() {
  return _this.drawFirstLine(currentAngle / 100);
});

它基本上是self = this为你做的this,@在函数内部或在函数内部this声明函数的时候.它非常方便,它可能是我最喜欢的coffeescript功能.