使用 iPhone/Objective C CGFloats：0.1 可以吗，还是应该是 0.1f？
当使用接受 CGFloat 的 iPhone Objective C 方法（例如 [UIColor colorWithRed:green:blue:]）时，将 af 附加到常量参数以显式指定它们是否很重要作为浮点数，例如在这种情况下我应该始终键入 0.1f 而不是 0.1 吗？或者编译器是否在编译时自动将 0.1（通常是双精度型）转换为 0.1f（这是浮点数）？我不希望在运行时发生这些转换，因为它们会不必要地占用性能。
预先感谢
MrMage
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.
Thanks in advance
MrMage
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这并不重要；在需要单精度常量的地方使用双精度常量不会破坏任何东西。
但是，如果您已打开有关隐式 64 位到 32 位转换的警告，并且正在为 32 位架构（我相信包括 iPhone）进行构建，那么您将需要简单地使用单精度常量以避免收到该警告。
（或者，您可以将该设置显式设置为关闭，并通过架构条件将其针对 64 位架构打开。但是，目前仅当您还在 Mac 中使用某些代码时才重要应用。）
It's not important; it won't break anything to use a double-precision constant where a single-precision constant is expected.
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.
(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.)