SCNVector3组件的类型是什么？ CGFloat还是Float？ [英] What is the type of SCNVector3 components? CGFloat or Float?

问题描述

Apple文档给出了SCNVector3的声明：

The apple documentation gives the declaration of SCNVector3 :

typedef struct SCNVector3 {CGFloat x，y，z; } SCNVector3;

typedef struct SCNVector3 { CGFloat x, y , z; } SCNVector3;

或者在尝试编写重载函数时：

Or when trying to write an overload function :

func * (left: SCNVector3, right: CGFloat) -> SCNVector3 {
    return SCNVector3Make(left.x * right, left.y * right, left.z * right)
}

我得到无法调用''的参数列表类型为错误。是不是left.x，left.y和left.z应该是CGfloat？

I get the "cannot invoke '' with an argument list of type" error. Aren't left.x, left.y and left.z supposed to be CGfloat ?

如果CGFloat是双重还是浮动，它是如何以及何时决定的？

How and when is it decided if CGFloat will be a double or a float?

推荐答案

在iOS 8.1 SDK标题中， SCNVectorX 类型基于在 Float 上，可以看到
通过命令点击 SCNVector3 ：

In the iOS 8.1 SDK headers, the SCNVectorX types are based on Float, as can be seen by command-clicking on SCNVector3:

struct SCNVector3 {
    var x: Float
    var y: Float
    var z: Float
}

func SCNVector3Make(x: Float, y: Float, z: Float) -> SCNVector3

这与OS X 10.10 SDK不同，其中 CGFloat 。所以文件
似乎是错误的。以下在iOS项目中编译：

This is different from the OS X 10.10 SDK where CGFloat is used. So the documentation seems to be wrong. The following compiles in an iOS project:

func * (left: SCNVector3, right: Float) -> SCNVector3 {
    return SCNVector3Make(left.x * right, left.y * right, left.z * right)
}

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