iOS 动态调用方法

示例：

- (void)bugly
{
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        if (NSClassFromString(@"Bugly")) {
            
            Class clazz = NSClassFromString(@"Bugly");
            SEL sel = NSSelectorFromString(@"startWithAppId:config:");
            IMP imp = [clazz methodForSelector:sel];
            void (*IMP_startWithAppId)(id, SEL, NSString *, id) = (void *)imp;
            
            NSDictionary *info = [[NSBundle mainBundle] infoDictionary];
            Class buglyConfig = NSClassFromString(@"BuglyConfig");
            id config = [[buglyConfig alloc]init];
            [config setValue:@"NO" forKey:@"debugMode"];
            [config setValue:[info objectForKey:(NSString *)kCFBundleIdentifierKey] forKey:@"channel"];
            [config setValue:[info objectForKey:(NSString *)kCFBundleNameKey] forKey:@"version"];
            
            IMP_startWithAppId(clazz, sel, BUGLY_KEY, config);
        }
    });
}

如上述示例代码，是对接Bugly的一段代码。我们APP里面并不需要导入bugly的类，通过拿到类的IMP ，来直接调用bugly的初始化方法，达到低耦合的目的。

在处理一些第三方框架或是服务的时候，建议这样处理比较灵活。

    Class clazz = NSClassFromString(@"XXXLoginViewController");
    SEL sel = NSSelectorFromString(@"sharedInstance");
    IMP imp = [clazz methodForSelector:sel];
    id (*setUserDataFunc)(id, SEL) = (void *)imp;
    id loginVC = setUserDataFunc(clazz,sel);
    UIButton * btn = [loginVC valueForKey:@"mobileValBtn"];

http://stackoverflow.com/questions/7017281/performselector-may-cause-a-leak-because-its-selector-is-unknown/20058585