实现一个单例

话不多说，直接撸代码
//================== LogManager.h ==================

@interface LogManager : NSObject

+(instancetype)sharedInstance;

- (void)printLog:(NSString *)logMessage;

- (void)uploadLog:(NSString *)logMessage;

@end

//================== LogManager.m ==================

@implementation LogManager

static LogManager* _sharedInstance = nil;

+(instancetype)sharedInstance
{
    static dispatch_once_t onceToken ;
    dispatch_once(&onceToken, ^{
        _sharedInstance = [[super allocWithZone:NULL] init] ;
    }) ;
    return _sharedInstance ;
}

+(id)allocWithZone:(struct _NSZone *)zone
{
    return [LogManager sharedInstance] ;
}

-(id)copyWithZone:(struct _NSZone *)zone
{
    return [LogManager sharedInstance];
}

-(id)mutableCopyWithZone:(NSZone *)zone
{
    return [LogManager sharedInstance];
}

- (void)printLog:(NSString *)logMessage{
    //print logMessage
}

- (void)uploadLog:(NSString *)logMessage{
    //upload logMessage
}

@end