Blocksの定義の引き数名は省略しない方がよい

// 引数名付きの定義
-(void)registerWithName:(NSString*)name
        completionBlock:(void (^)(NSString* accessToken, NSError* error)) completionBlock;

// 補完入力後、特に引き数名を変えない場合はblocksの処理だけ書けばよい
    [self registerWithName:@"fuga"
           completionBlock:^(NSString *accessToken, NSError *error) {

    }];

// 引数名省略の定義
-(void)registerWithName:(NSString*)name
        completionBlock:(void (^)(NSString* , NSError* )) completionBlock;

// 補完入力後、わざわざ引き数名を自分で打つのが面倒くさい
    [self registerWithName:@"fuga"
           completionBlock:^(NSString *, NSError *) {
    }];