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问题描述
我有一个类Transaction,其类型为Int的可变金额. 我想从另一个有array of Transactions的类中访问它,并对它们的全部金额求和.
I have a class Transaction which has a var amount of type Int. I want to access it from another class, where I have an array of Transactions and sum all of their amounts.
所以我有这段代码
func computeTotal()-> Int{ let total = 0 for transaction in transactions{ //get the amounts of each and sum all of them up total += transaction.amount } return total }但这给我一个错误
无法使用类型为(Int,@value Int)的参数列表调用"+ ="
是什么原因引起的?我知道在Swift中,两个操作数必须是同一类型,但是在我的代码中它们都是Int类型.
What can cause that? I know that in Swift both operands must be the same type, but they are both of type Int in my code.
推荐答案let创建不可变的值.您需要使用var,例如:
let creates an immutable value. You need to use var, like:
func computeTotal()-> Int{ var total = 0 for transaction in transactions{ //get the amounts of each and sum all of them up total += transaction.amount } return total }更多推荐
无法调用"+ ="参数类型为(Int,@value Int)的参数列表
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