无法识别的选择器问题

Question

我很困惑......我有这个函数"colorWithHexString"...当我将它包含在调用它的viewcontroller中时,它工作正常.但是当我将它移动到一个单独的"BSJax"类并使用相同的输入参数调用它时,它会抛出一个无法识别的选择器错误.这是电话:

BSjax *bsjax = [BSjax new];
NSString *hexString = [NSString stringWithString:@"CCCCFF"];
[self.view setBackgroundColor:[bsjax colorWithHexString:hexString]];

我很确定我正在调用函数的方式阻止它作为bsjax方法工作.任何反馈将不胜感激.

BSjax.h包括:

+ (UIColor *)colorWithHexString:(NSString *)stringToConvert;

......和BSjax.m包括:

+ (UIColor *)colorWithHexString:(NSString *)stringToConvert
{
    NSString *cString = [[stringToConvert stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] uppercaseString];

    // String should be 6 or 8 characters
    if ([cString length] < 6) NSLog(@"colorWithHexString called with parameter < 6 characters in length");

    // strip 0X if it appears
    if ([cString hasPrefix:@"0X"]) cString = [cString substringFromIndex:2];

    if ([cString length] != 6) NSLog(@"colorWithHexString called with parameter != 6 characters in length");

    // Separate into r, g, b substrings
    NSRange range;
    range.location = 0;
    range.length = 2;
    NSString *rString = [cString substringWithRange:range];

    range.location = 2;
    NSString *gString = [cString substringWithRange:range];

    range.location = 4;
    NSString *bString = [cString substringWithRange:range];

    // Scan values
    unsigned int r, g, b;
    [[NSScanner scannerWithString:rString] scanHexInt:&r];
    [[NSScanner scannerWithString:gString] scanHexInt:&g];
    [[NSScanner scannerWithString:bString] scanHexInt:&b];

    return [UIColor colorWithRed:((float) r / 255.0f)
                           green:((float) g / 255.0f)
                            blue:((float) b / 255.0f)
                           alpha:1.0f];
}

Answer 1

您正在尝试在实例上调用类方法.

注意+:

+ (UIColor *)colorWithHexString:(NSString *)stringToConvert;

这意味着你只能将方法称为 [ClassName classmethod]

然后在这里您尝试将该方法与实例一起使用[instanceObject classmethod]:

BSjax *bsjax = [BSjax new];
[self.view setBackgroundColor:[bsjax colorWithHexString:hexString]];

尝试将其更改为:

[self.view setBackgroundColor:[BSjax colorWithHexString:hexString]];

这应该让你直截了当.