如何定义UIColor的常量值？ [英] How do I define constant values of UIColor?

问题描述

我想这样做，但我不能得到一个合作的语法。

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，但它们是丑陋的。

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，用这种方法的新方法。这里是我今天写的代码片段：

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

例如：

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

和我自己定义的颜色合并在系统定义的颜色旁边。

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

（顺便提一句，我开始更多地考虑HSB而不是RGB，因为我更注意颜色。）

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

UPDATE about precomputing the value：我的预感是，它不值得。但是如果你真的想要，你可以用静态变量记住值：

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;
}

你可以做一个宏做记忆。

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

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