斯威夫特 - 麻烦来自追加数组类 [英] Swift - trouble appending array from class

问题描述

我无法理解为什么以下code与最新信息替换所有的数组元素，当我试图只是其追加。

I am having trouble understanding why the following code is replacing all of my array elements with the latest information when I am trying to just append it.

我有以下类：

class usersAvailable {
    var username = String()
    var userAvatar = UIImage()
}

我定义为使用类以下变量：

I have the following variables defined to use the class:

//the array which will hold users available to follow
    var usersAvailableArray = [usersAvailable]()
    var aUser = usersAvailable()

要检查我的理智我也已经宣布国家进入常规阵，看看我得到正确的价值观：

to check my sanity I also have declared a 'regular' array to see if I am getting the right values:

var usersArray:[[String]] = [["",""]]

当我执行以下code：

when i execute the following code:

func getAllUsers() {

        usersAvailableArray.removeAll(keepCapacity: true)
        usersArray.removeAll(keepCapacity: true)
        var query = PFQuery(className: "_User")
        query.findObjectsInBackgroundWithBlock {
            (objects: [AnyObject]?, error: NSError?) -> Void in
            if error == nil {
                for object in objects! {
                  self.aUser.username = object["username"] as! String
                    println("aUser.username before append: \(self.aUser.username)")
                    println(self.aUser)
                    self.usersAvailableArray.append(self.aUser)
                    self.usersArray.append([self.aUser.username])
                    println("first element of usersAvailableArray: \(self.usersAvailableArray.first?.username)")
                    println("last element of usersAvailableArray: \(self.usersAvailableArray.last?.username)")
                    println("number of elements currently in usersAvailableArray: \(self.usersAvailableArray.count)")
                    println("first element of usersArray: \(self.usersArray.first)")
                    println("last element of usersArray: \(self.usersArray.last)")
                    println("number of elements currently in usersArray: \(self.usersArray.count)")
 }

这里是控制台输出我得到：

here is the console output I get:

aUser.username before append: joeBob
ParseStarterProject.usersAvailable
first element of usersAvailableArray: Optional("joeBob")
last element of usersAvailableArray: Optional("joeBob")
number of elements currently in usersAvailableArray: 1
first element of usersArray: Optional(["joeBob"])
last element of usersArray: Optional(["joeBob"])
number of elements currently in usersArray: 1
aUser.username before append: monkey
ParseStarterProject.usersAvailable
first element of usersAvailableArray: Optional("monkey")
last element of usersAvailableArray: Optional("monkey")
number of elements currently in usersAvailableArray: 2
first element of usersArray: Optional(["joeBob"])
last element of usersArray: Optional(["monkey"])
number of elements currently in usersArray: 2
aUser.username before append: support
ParseStarterProject.usersAvailable
first element of usersAvailableArray: Optional("support")
last element of usersAvailableArray: Optional("support")
number of elements currently in usersAvailableArray: 3
first element of usersArray: Optional(["joeBob"])
last element of usersArray: Optional(["support"])
number of elements currently in usersArray: 3

为什么我的usersAvailableArray更换阵列UsersAvailableArray中的每个元素的追加？

Why is my append of usersAvailableArray replacing every element in the array UsersAvailableArray?

推荐答案

正在传递数据通过引用数组中，并在每个循环中，您更改参考值：

You are passing data to the array by reference, and in every loop you change the value of the reference:

self.aUser.username = object["username"] as! String
self.usersAvailableArray.append(self.aUser)

试着每次创建新用户：

Try to create a new user every time:

var newUser = usersAvailable()
newUser.username = object["username"] as! String
self.usersAvailableArray.append(newUser)

这是发生因为对象是你从追加一个类来，从<一个href=\"https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/ClassesAndStructures.html\"相对=nofollow> APPE文档：

This is happening because the object you are append come from a class, from appe documentation:

类是引用类型

与值类型，引用类型而不是当他们被复制
  分配给一个变​​量或常数，或当它们被传递给
  功能。而不是副本，以相同的参考现有
  实例代替。你可以看到更多的价值和引用
  在斯威夫特

Unlike value types, reference types are not copied when they are assigned to a variable or constant, or when they are passed to a function. Rather than a copy, a reference to the same existing instance is used instead. You can see more about values and references in Swift

另一个解决方案是你的类变成一个结构，如下图所示，结构不同，如果类使得当它被传递，而不是通过一个参考值的副本。

Another solution is to change your class to a struct, like below, structs different if classes make a copy of the value when it is passes instead pass a reference.

struct usersAvailable {
    var username = String()
    var userAvatar = UIImage()
}

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