objective-c - 为什么我的 NSColor 类 NSConcreteData？

Question

在数据模型中，我将颜色定义为可转换属性，并将 ColorTransformer 分配给它。它可以工作，在同一个变压器的帮助下，我可以将它绑定(bind)到 ColorPicker，保存和打开文档。 但是当我尝试从代码访问它时:

NSColor * color = corner.color;
NSLog(@"Corner Color = %@\n%@", color, color.class);

我有 NSMutableConcreteData 对象:

bezierMesh[22164:730708] Corner Color = <040b7374 7265616d 74797065 6481e803 84014084 8484074e 53436f6c 6f720084 84084e53 4f626a65 63740085 84016301 84046666 66660183 6eb7613d 8357703e 3e8352b8 1e3f86>
NSConcreteMutableData

修改 getter 和 setter 没有帮助:

- (NSColor *)color {

    [self willAccessValueForKey:@"color"];
    NSData *colorData = [self primitiveValueForKey:@"color"];
    [self didAccessValueForKey:@"color"];
    if (colorData == nil) {
        return nil;
    }


   NSColor * color = [NSKeyedUnarchiver unarchiveObjectWithData:colorData];
   return color;
   }

- (void)setColor:(NSColor *)color {
    NSLog(@" -------------- > Setting color %@", color);
     NSData * theData=[NSArchiver archivedDataWithRootObject:color];
    [self willChangeValueForKey:@"color"];
    [self setPrimitiveValue:theData forKey:@"color"];
    [self didChangeValueForKey:@"color"];
}

它会导致错误:

[NSKeyedUnarchiver initForReadingWithData:]: non-keyed archive cannot be decoded by NSKeyedUnarchiver

如何获取颜色NSColor？

Answer 1

这是我不久前编写的一个 NSString <-> NSColor 转换器，它旨在使用 NSUserDefaults 中的 RGB 值存储颜色因为我不喜欢默认使用 NSData 对象:

StringColourTransformer.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 [NSColor 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

如您所见，我提供了几个类方法，以便更轻松地从代码中使用它(toString 和 fromString)。

它需要在应用程序生命周期的早期注册，以便可以用于转换 IB 内的值(这是从单例中调用的，其中 _stringColourTransformer 是实例变量):

_stringColourTransformer = [[StringColourTransformer alloc] init];
[NSValueTransformer setValueTransformer:_stringColourTransformer
                                forName:@"StringColourTransformer"];

转换非常简单:

NSColor *colour = [StringColourTransformer fromString:@"1.0 1.0 0.0 1.0"];

注意:现在查看代码，我可能会在 toString/fromString 方法中使用 [NSValueTranformer valueTransformerForName:]，而不是创建每次都有一个新实例。可能更便宜。