Objective-C方法参数问题

问题描述

我正在尝试定义一种非常简单的实用程序方法，它将使我不必使用计算器将RGB值定义为百分比.当我查看Apple的示例代码"QuartzCache"时，在DrawView.m文件的第96行中，我看到了以下内容:

I'm attempting to define an extremely simple utility method that will save me from having to use a calculator to define RGB values as percentages. When I look into Apple's sample code called "QuartzCache", in the DrawView.m file, line 96, I see this:

float whiteColor[4] = {1, 1, 1, 1};

但是，当我尝试创建如下所示的方法时，编译器讨厌我.半小时的强化Google搜寻没有产生任何帮助.

However, when I attempt to created a method like the following, the compiler hates me. A half-hour of intensive Googling has not produced any help.

 +(float[])percentagesRGBArray:(float[])rgbArray{

        float red = rgbArray[0];
        float green = rgbArray[1];
        float blue = rgbArray[2];
        float alpha = rgbArray[3];
        red = red/255;
        green = green/255;
        blue = blue/255;
        alpha = alpha;
        float percentagesRGBArray[4] = {red, green, blue, alpha};


        return  percentagesRGBArray;
    }

定义这种方法的正确方法是什么?我在这里做错了什么?

What is the proper way to define such a method? What am I doing wrong here?

推荐答案

定义包含所有组件的struct，或将每个单独的组件包装在NSNumber中.或者，使用NSColor实例包含您的颜色分量.

Define a struct that contains all of the components, or wrap up each individual component in an NSNumber. Alternatively, use an NSColor instance to contain your colour components.

• struct方式:

typedef struct
{
    float red;
    float green;
    float blue;
    float alpha;
} MyColor;

- (MyColor) percentagesRGBArray:(MyColor) incoming
{
    MyColor result;
    result.red = incoming.red / 255;
    result.green = incoming.green / 255;
    result.blue = incoming.blue / 255;
    result.alpha = incoming.alpha;
    return result;
}

NSNumber方式:

- (NSArray *) percentagesRGBArray:(float[]) rgbArray
{
    NSNumber *red = [NSNumber numberWithFloat:rgbArray[0] / 255];
    NSNumber *green = [NSNumber numberWithFloat:rgbArray[1] / 255];
    NSNumber *blue = [NSNumber numberWithFloat:rgbArray[2] / 255];
    NSNumber *alpha = [NSNumber numberWithFloat:rgbArray[3]];

    return [NSArray arrayWithObjects:red, green, blue, alpha, nil];
}

NSColor方式:

- (NSColor *) percentagesRGBArray:(float[]) rgbArray
{
    CGFloat red = rgbArray[0] / 255;
    CGFloat green = rgbArray[1] / 255;
    CGFloat blue = rgbArray[2] / 255;
    CGFloat alpha = rgbArray[3];

    return [NSColor colorWithDeviceRed:red
                                 green:green
                                  blue:blue
                                 alpha:alpha];
}

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