爲什麼具有兩個操作數的語句需要在具有一個操作數的語句之上才能正確輸出？

Question

當我創建不正確的屬性，並把

else if username != "tigerclaw" && password != "888love" { 
print("Re-enter username and password") 
} 

在我的塊的Xcode的底部不會打印出「重新輸入用戶名和密碼」時輸入不正確。

是否因爲具有相同數量操作數的語句需要一個接一個？因爲這有效。

let username: String = "2igerclaw" 
let password: String = "x88love" 

if username == "tigerclaw" && password == "888love" { 
print("Acess Granted") 

} else if username != "tigerclaw" && password != "888love" { 
print("Re-enter username and password") 


} else if username != "tigerclaw" { 
print("Re-enter username") 

} else if password != "888love" { 
print("Re-enter password") 

} 

Answer 1

您正在使用else if來連接所有這些語句。當您使用else語法時，只有先前條件未評估爲true時纔會檢查條件。例如：

if (true) { 
    // This code will execute because true is, well true. 
} else (true) { 
    // This code WILL NOT execute, because the else statement will never be checked because we fell inside the first conditional. 
} 

如果您想要同時執行這兩個操作，那麼您需要將這些語句分開。例如：

if (true) { 
    // This will be excuted because true is, well true. 
} 

if (true == true) { 
    // This will also be executed because true is still true and we are not limiting it by the else. 
}