Question

如何从viewcontroller发送变量以由另一个viewcontroller修改？

我已经尝试在performSegue中设置变量，但它没有被修改。

示例代码：

class VC1: ViewController{
    var myVar: MyVar

    ....
    prepare(for segue:...) {
        let nextVC = segue.destination as! VC2
        nextVC.var = myVar
    }
    ....
}


class VC2: ViewController {
    var var: MyVar

    ....
    override func viewDidLoad() {
        super.viewDidLoad()
        var = MyVar("newValue")
    }
}

执行此代码后，VC1中myVar的值不会更改为新值。我相信它只会得到myVar的浅层副本，而不是深层副本。

我想要在swift中实现什么？

Answer 1

Swift中的类是通过引用传递的，而结构是按值传递的。假设MyVar是一个类，您需要修改类的属性，即：

myVar.property = "xyz"

而不是像你在问题中那样定义一个新的类实例。

Answer 2

设置var时，会将新实例分配给# extract the part that interest us grok { match => { "message" => "%{GREEDYDATA}Metrics :\[%{GREEDYDATA:Metrics}\]" } } # divide each event in multiple events, depending on the contents of the Metrics field split { field => "Metrics" terminator => "], Metric [" target => "metric" } # removing things left behind when splitting the Metrics field. mutate { gsub => ["metric", "Metric \[", "", "metric", "\]", ""] } # apply the kv filter, extracting key-value pairs from the metric field kv { source => "metric" field_split => "," }。

Answer 3

在游乐场中检查以下代码的结果。它应该让您更深入地了解您应该期待什么，而不会出现segue和控制器的复杂性。

class Variable {
    var name:String

    init(_ nameString:String) {
        name = nameString
    }
}

class Sender {
    var myVar = Variable("Start name")

    func showChanges() {
        let receiver = Receiver(myVar)
        print(myVar.name)
        receiver.modify()
        print(myVar.name)
        receiver.replace()
        print(myVar.name)
    }
}

class Receiver {
    var received: Variable

    init(_ variable:Variable) {
        received = variable
    }

    func modify() {
        received.name = "Changed name"
    }

    func replace() {
        received = Variable("New variable")
    }
}

let s = Sender()
s.showChanges()

在另一个类中发送要修改的变量？

3 个答案: