爲什麼我的代碼在counterLabel.text變量的第二個+號上拋出一個二元運算符錯誤？

Question

此代碼在計數器Label.text變量的第二個+符號上拋出錯誤「Binary Operator'+'不能應用於'String'和'Double'類型的操作數。如果我在計數器Label.text中的minutesLabel後面刪除所有內容，則錯誤將消失（這是用Swift編寫的）。也對任何格式混淆抱歉我是第一次使用。

func updateCounter(timer: NSTimer) { 

     let hours = floor(stopWatchTime/pow(60, 2)) 
     let hoursInSeconds = hours * pow(60, 2) 

     let minutes = floor((stopWatchTime - hoursInSeconds)/60) 
     let minutesInSeconds = minutes * 60 

     let seconds = floor((stopWatchTime - hoursInSeconds - minutesInSeconds)/60) 
     let secondsInCentiseconds = seconds * 100 

     let centiseconds = stopWatchTime - hoursInSeconds - minutesInSeconds - secondsInCentiseconds 

     let hoursLabel = String(format: "%02.0f:", hours) 
     let minutesLabel = String(format: "%02.0f:", minutes) 
     let secondsLabel = String(format: "%02.0f:", seconds) 
     let centisecondsLabel = String(format: "%02.0f", centiseconds) 

     counterLabel.text = hoursLabel + minutesLabel + secondsLabel + centiseconds 

     stopWatchTime = stopWatchTime + 1 

Answer 1

你忘了標籤添加到變量centiseconds，因爲它不是字符串，centisecondsLabel是String。那就是爲什麼你得到了二元運算錯誤。 使用下面的代碼：

counterLabel.text = hoursLabel + minutesLabel + secondsLabel + centisecondsLabel 

，將解決這個問題！