通过#色值方式设置颜色

+ (UIColor *)colorWithRGB:(NSString *)rgbstr{
    NSString *newrgbstr = [rgbstr uppercaseString];
    NSInteger strlen = newrgbstr.length;
    UIColor *color = nil;
    unichar first = [newrgbstr characterAtIndex:0];
    if (first == '#') {
        for (int i = 1; i < strlen; i++) {
            unichar u = [newrgbstr characterAtIndex:i];
            if (!(u >= '0' && u <= '9') && !(u >= 'A' && u <='F')) {
                NSString *exName = [NSString stringWithFormat:@"使用%@类获取指定颜色错误", NSStringFromClass([self class])];
                NSException *e = [NSException exceptionWithName:exName reason:@"请检查颜色数值越界" userInfo:nil];
                @throw e;
            }
        }
        if (newrgbstr.length == 4) {
            unichar uarray[3];
            for(int i = 0;i < 3;i++){
                uarray[i] = [newrgbstr characterAtIndex:(i+1)];
            }
            for (int i = 0;i < 3;i++) {
                uarray[i] = (uarray[i] > '9' ? (uarray[i]-'A'+10) : (uarray[i]-'0')) * 17 % 256;
            }
            CGFloat r = uarray[0]/255.0f;
            CGFloat g = uarray[1]/255.0f;
            CGFloat b = uarray[2]/255.0f;
            color = [UIColor colorWithRed:r green:g blue:b alpha:1];
        }else if(newrgbstr.length == 7){
            unichar uarray[6];
            for(int i = 0;i < 6;i++){
                uarray[i] = [newrgbstr characterAtIndex:(i+1)];
            }
            for (int i = 0;i < 3;i++) {
                unichar l = uarray[2*i];
                unichar r = uarray[2*i+1];
                uarray[i] = ((l > '9' ? (l-'A'+10) : (l-'0')) * 16 +
                             (r > '9' ? (r-'A'+10) : (r-'0'))) % 256;
            }
            CGFloat r = uarray[0]/255.0f;
            CGFloat g = uarray[1]/255.0f;
            CGFloat b = uarray[2]/255.0f;
            color = [UIColor colorWithRed:r green:g blue:b alpha:1];
        }
    }
    return color;
}

可以通过#fff和#ffffff两种方式设置色值，和设计协调更方便