[iOS]UIAlertController修改提示按钮文字颜色

 系统提示按钮字体颜色默认是蓝色，因为是在项目优化时产生的需求故使用拓展的方式解决。

#import "UIAlertController+GSActionBtn.h"

@implementation UIAlertController (GSActionBtn)

+ (void)load {
    // 只执行一次
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        [NSObject exchangeInstanceMethodWithSelfClass:UIAlertController.class originalSelector:@selector(addAction:) swizzledSelector:@selector(GSActionBtn_AddAction:)];
    });
}

- (void)GSActionBtn_AddAction:(UIAlertAction *)action {
    if ([action.title isEqualToString:@"取消"] && self.preferredStyle == UIAlertControllerStyleAlert) {
        UIColor *tempColor = [UIColor colorWithRed:51/255.0 green:51/255.0 blue:51/255.0 alpha:1];
        [action setValue:tempColor forKey:@"_titleTextColor"];
    }
    [self GSActionBtn_AddAction:action];
}

@end

示意图