如何定义 UIColor 的常量值?

How do I define constant values of UIColor?(如何定义 UIColor 的常量值?)

问题描述

我想做这样的事情，但我无法获得合作语法.

I want to do something like this, but I cannot get a cooperative syntax.

static const UIColor *colorNavbar = [UIColor colorWithRed: 197.0/255.0 green: 169.0/255.0 blue: 140.0/255.0 alpha: 1.0];

我想我可以定义宏，但它们很丑.

I suppose that I could define macros, but they are ugly.

推荐答案

我喜欢使用类别来扩展类，并为这类事情提供新方法.下面是我今天刚刚写的一段代码:

I like to use categories to extend classes with new methods for this sort of thing. Here's an excerpt of code I just wrote today:

@implementation UIColor (Extensions)

+ (UIColor *)colorWithHueDegrees:(CGFloat)hue saturation:(CGFloat)saturation brightness:(CGFloat)brightness {
    return [UIColor colorWithHue:(hue/360) saturation:saturation brightness:brightness alpha:1.0];
}

+ (UIColor *)aquaColor {
    return [UIColor colorWithHueDegrees:210 saturation:1.0 brightness:1.0];
}

+ (UIColor *)paleYellowColor {
    return [UIColor colorWithHueDegrees:60 saturation:0.2 brightness:1.0];
}

@end

现在我可以在代码中执行以下操作:

Now in code I can do things like:

self.view.backgroundColor = highlight? [UIColor paleYellowColor] : [UIColor whitecolor];

我自己定义的颜色与系统定义的颜色完全吻合.

and my own defined colors fit right in alongside the system-defined ones.

(顺便说一句，我开始更多地考虑 HSB 而不是 RGB，因为我更关注颜色.)

(Incidentally, I am starting to think more in terms of HSB than RGB as I pay more attention to colors.)

关于预先计算价值的更新:我的直觉是它不值得.但如果你真的想要，你可以用静态变量来记忆值:

UPDATE regarding precomputing the value: My hunch is that it's not worth it. But if you really wanted, you could memoize the values with static variables:

+ (UIColor *)paleYellowColor {
    static UIColor *color = nil;
    if (!color) color = [UIColor colorWithHueDegrees:60 saturation:0.2 brightness:1.0];
    return color;
}

你也可以制作一个宏来做记忆.

You could make a macro do do the memoizing, too.

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