从字符串中取颜色

+ (UIColor *)colorWithString:(NSString *)stringToConvert {

NSScanner *scanner = [NSScanner scannerWithString:stringToConvert];

if (![scanner scanString:@"{" intoString:NULL]) return nil;

const NSUInteger kMaxComponents = 4;

CGFloat c[kMaxComponents];

NSUInteger i = 0;

if (![scanner scanFloat:&c[i++]]) return nil;

while (1) {

if ([scanner scanString:@"}" intoString:NULL]) break;

if (i >= kMaxComponents) return nil;

if ([scanner scanString:@"," intoString:NULL]) {

if (![scanner scanFloat:&c[i++]]) return nil;

} else {

// either we're at the end of there's an unexpected character here

// both cases are error conditions

return nil;

}

}

if (![scanner isAtEnd]) return nil;

UIColor *color;

switch (i) {

case 2: // monochrome

color = [UIColor colorWithWhite:c[0] alpha:c[1]];

break;

case 4: // RGB

color = [UIColor colorWithRed:c[0] green:c[1] blue:c[2] alpha:c[3]];

break;

default:

color = nil;

}

return color;

}

+ (UIColor *)randomColor {

return [UIColor colorWithRed:(CGFloat)RAND_MAX / random()

  green:(CGFloat)RAND_MAX / random()

blue:(CGFloat)RAND_MAX / random()

  alpha:1.0f];

}