objective-c - 将 NSString 转换为 UIColor

Question

我有一个充满 NSString 的数组，我需要使用 NSString 来更改属性文本的颜色。我将原始 NSString 分成一个包含单个 NSString 和颜色的数组，但我被困在这里。数组中的字符串是 [UIColor Orangecolor]。我已经尝试过，但它返回 null。

 SEL blackSel = NSSelectorFromString(@"blackColor");
 UIColor* tColor = nil;
if ([UIColor respondsToSelector: blackSel])
  tColor  = [UIColor performSelector:blackSel];

Answer 1

我编写了一个自定义的 NSValueTransformer 来允许我将 NSColor 转换为 NSString(并返回)以存储到 NSUserDefaults 因为我不喜欢使用字节数组存储颜色，这是默认行为。如果您在 IB 中设置自定义变压器，它也可以跨 KVO 使用。当然，您也可以在代码中调用静态方法来执行转换。

针对 UIColor 进行修改应该不会花费很多工作:

StringColourTransformer.h:

#import <Cocoa/Cocoa.h>

@interface StringColourTransformer : NSValueTransformer

+ (NSString *)toString:(NSColor *)value;
+ (NSColor *)fromString:(NSString *)value;

@end

StringColourTransformer.m:

#import "StringColourTransformer.h"

@implementation StringColourTransformer

+ (NSString *)toString:(NSColor *)value
{
    StringColourTransformer *transformer = [[StringColourTransformer alloc] init];
    NSString *str = [transformer reverseTransformedValue:value];
    return str;
}

+ (NSColor *)fromString:(NSString *)value
{
    StringColourTransformer *transformer = [[StringColourTransformer alloc] init];
    NSColor *color = (NSColor *)[transformer transformedValue:value];
    return color;
}

+ (Class)transformedValueClass
{
    return [NSString class];
}

+ (BOOL)allowReverseTransformation
{
    return YES;
}

- (id)transformedValue:(id)value
{
    CGFloat r = 0.0, g = 0.0, b = 0.0, a = 1.0;

    // Only NSString classes are reverse-transformed
    if ([value isKindOfClass:[NSString class]])
    {
        NSString *stringValue = (NSString *)value;
        sscanf([stringValue UTF8String],
#ifdef __x86_64
               "%lf %lf %lf %lf",
#else
               "%f %f %f %f",
#endif
               &r, &g, &b, &a);
    }

    return [NSColor colorWithCalibratedRed:r green:g blue:b alpha:a];
}

- (id)reverseTransformedValue:(id)value
{
    CGFloat r = 0.0, g = 0.0, b = 0.0, a = 1.0;

    // Only NSColor classes are transformed
    if ([value isKindOfClass:[NSColor class]])
    {
        NSColor *colourValue = (NSColor *)value;
        NSColor *converted = [colourValue colorUsingColorSpaceName:@"NSCalibratedRGBColorSpace"];
        [converted getRed:&r green:&g blue:&b alpha:&a];
    }

    return [NSString stringWithFormat:@"%.3f %.3f %.3f %.3f", r, g, b, a];
}

@end