使用for循环显示4个纹理

I'm creating a game using Swift 2.0 and Sprite-Kit with Xcode7. I want to implement 4 purple balls that are suppose to resemble lives. So every time the player gets hit he loses one purple ball. They are supposed to appear side by side. I was wondering if instead of hardcoding 4 balls on to the scene I could instead use a for loop to display 4 balls.

我正在使用Swift 2.0和Sprite-Kit与Xcode7创建游戏。我想实现4个紫色球，假设它们类似于生命。所以每次球员被击中时他都会失去一个紫色的球。他们应该并排出现。我想知道如果不是硬编码4个球到现场我可以改为使用for循环来显示4个球。

let purpleBall = SKSpriteNode(texture: purpleTexture)
purpleBall.position = CGPointMake(self.frame.size.width * 0.65, self.frame.size.height * 0.92)
self.addChild(purpleBall)

I haven't been successful on getting 4 balls to appear on the scene. This was one of my attempts.

我没有成功让4个球出现在现场。这是我的一次尝试。

for(var i = 0.50; i <= 0.90; i = i + 0.10) {
        let purpleBall = SKSpriteNode(texture: purpleTexture)
        purpleBall.position = CGPointMake(self.frame.size.width * i, self.frame.size.height * 0.92)
        self.addChild(purpleBall)
}

Here I get an error: Binary operator cannot be applied to operands of type 'CGFloat' and 'Double' Do I have to convert i to CGFloat? and will this code actually place 4 different balls side by side or only move the single one to each new position.

这里我得到一个错误：二进制运算符不能应用于'CGFloat'和'Double'类型的操作数我是否必须将i转换为CGFloat？并且这段代码实际上会并排放置4个不同的球，或者只将单个球移动到每个新位置。

1 个解决方案

#1

Your code has an off by one error in the for loop. It should be a less than sign rather than less than or equal too. Your current code is going to create five purple balls.

您的代码在for循环中有一个错误。它应该小于符号而不是小于或等于。您当前的代码将创建五个紫色球。

You shouldn't really let i equal anything but an integer it's confusing. You could rewrite the code like this and it would do the same thing, without the worry of the float/double errors you're currently getting. Note that I will also use a constant called maxBalls, and distanceBetweenBalls so that you can easily change the number of balls and the distance without any complicated rewriting:

你不应该让我相等，只是一个整数令人困惑。你可以像这样重写代码，它会做同样的事情，而不用担心你目前得到的浮动/双重错误。请注意，我还将使用一个名为maxBalls和distanceBetweenBalls的常量，以便您可以轻松更改球的数量和距离，而无需任何复杂的重写：

let maxBalls = 4
for(var i = 0; i < maxBalls; i++) {
    let purpleBall = SKSpriteNode(texture: purpleTexture)
    let ballXPosition = .50 + (i * .1)
    purpleBall.position = CGPointMake(self.frame.size.width * ballXPosition, self.frame.size.height * 0.92)
    self.addChild(purpleBall)

This should avoid the issues you were facing before, hope that helps.

这应该避免你以前遇到的问题，希望有所帮助。

#1