使用iPhone / Objective C CGFloats：是0.1还是应该是0.1f？ [英] Using iPhone/Objective C CGFloats: Is 0.1 okay, or should it be 0.1f?

问题描述

当使用接受 CGFloat 的iPhone Objective C方法，例如 [UIColor colorWithRed：green：blue：] ，重要的是将f附加到常量参数以明确指定为浮动，例如。在这种情况下，我应该总是输入0.1f而不是0.1？或者编译器自动将0.1（这是一般的两倍）转换为0.1f（这是一个浮点数）在编译时？我不希望这些演员在运行时发生，因为他们将不必要地表演。

When using an iPhone Objective C method that accepts CGFloats, e.g. [UIColor colorWithRed:green:blue:], is it important to append a f to constant arguments to specifiy them explicitly as floats, e.g. should I always type 0.1f rather than 0.1 in such cases? Or does the compiler automatically cast 0.1 (which is a double in general) to 0.1f (which is a float) at compile time? I don't wish to have these casts happen at run time because they would unneccessarily hog performance.

提前感谢

MrMage

推荐答案

这不是重要的;它不会破坏任何使用双精度常数的单精度常数预期。

It's not important; it won't break anything to use a double-precision constant where a single-precision constant is expected.

但是，如果您已经打开关于隐式64位的警告，位32位转换，正在构建32位体系结构（我相信包括iPhone），那么您将需要使用单精度常量来避免发生警告。

However, if you have turned on the warning about implicit 64-bit-to-32-bit conversions and are building for 32-bit architectures (which I believe includes the iPhone), then you'll want to use single-precision constants simply to avoid getting that warning.

（或者，您可以将该设置设置为明确关闭，架构条件使64位体系结构处于开启状态，但目前 仅当您也是在Mac应用程序中使用一些代码。）

(Alternatively, you could set that setting to explicitly off, with an architecture condition turning it on for 64-bit architectures. But that currently only matters if you're also using some of your code in a Mac application.)

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