arrays - 在swift中找到后修改数组元素不起作用

Question

我写了一个这样的模型作为练习:

struct Store {
    var name : String
    var bills : Array<Bill>
    var category : Category?
}

struct Bill {
    var date : String
    var amount : Float
}

struct Category {
    var name : String
    var tags : Array<String>
}

当我搜索商店是否已存在并向其添加账单而不是创建新商店时，我的代码不起作用。它的行为就像搜索结果是数组元素的副本一样。我想要一个引用。

var stores : Array <Store> = Array()
for billStatment in billStatements! {
    let billParts = billStatment.split(separator: ",")
    if billParts.count > 0 {
        let bill : Bill = Bill(date:String(billParts[0]), amount: Float(billParts[2])!)
        var store : Store = Store(name:String(billParts[1]), bills: [bill], category: nil)


        if var alreadyAddedStore = stores.first(where: {$0.name == String(billParts[1])}) {
            alreadyAddedStore.bills.append(bill)
            print("yeah found it \(alreadyAddedStore)") // the debugger breaks here so I know the "first" method is working. If I print alreadyAddedStore here I have one more element, that's fine.
        } else {
            stores.append(store)
        }

    }
}

 print("\(stores.count)") // If I break here for a given store that should contains multiple elements, I will see only the first one added in the else statement.

谁能告诉我我做错了什么？

Answer 1

如前所述，您将值(结构)语义与引用(类)语义混淆了。

一个简单的修复方法是将更改存储到以名称作为键的字典中:

var stores : Dictionary<String, Store> = [:]

并像这样使用它:

if(stores[store.name] == nil) {
    stores[store.name] = store
}
else {
    stores[storeName].bills.append(bill)
}