主線程刷新UI

dispatch_async(dispatch_get_main_queue(), ^{
        ///
});

單例

static Tools *_sharedManger;

@implementation Tools

+ (SingleTools *)sharedManger{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        if (!_sharedManger) {
            _sharedManger = [[Tools alloc]init];
        }
        
    });
    
 
return _sharedManger;
}

@end

iOS-主線程刷新UI【+單例】