如何使用fyne避免GUI應用程式中的回圈依賴？

我想將 GUI 添加到我用 Go 撰寫的命令列應用程式中，但我遇到了 fyne 和回圈依賴項的問題。

考慮這個簡單的例子來說明我面臨的問題：假設一個按鈕在我的模型類上觸發了一個耗時的方法（比如獲取資料左右），我希望在任務完成時更新視圖。

我首先實作了一個非常幼稚且完全不解耦的解決方案，這顯然會遇到 go 編譯器引發的回圈依賴錯誤。考慮以下代碼：

main.go

package main

import (
    "my-gui/gui"
)

func main() {
    gui.Init()
}

gui/gui.go

package gui

import (
    "my-gui/model"
    //[...] fyne imports
)

var counterLabel *widget.Label

func Init() {
    myApp := app.New()
    myWindow := myApp.NewWindow("Test")

    counterLabel = widget.NewLabel("0")

    counterButton := widget.NewButton("Increment", func() {
        go model.DoTimeConsumingStuff()
    })

    content := container.NewVBox(counterLabel, counterButton)

    myWindow.SetContent(content)
    myWindow.ShowAndRun()
}

func UpdateCounterLabel(value int) {
    if counterLabel != nil {
        counterLabel.SetText(strconv.Itoa(value))
    }
}

模型/模型.go

package model

import (
    "my-gui/gui" // <-- this dependency is where it obviously hits the fan
    //[...]
)

var counter = 0

func DoTimeConsumingStuff() {
    time.Sleep(1 * time.Second)
    
    counter  

    fmt.Println("Counter: "   strconv.Itoa(counter))
    gui.UpdateCounterLabel(counter)
}

所以我想知道如何正確解耦這個簡單的應用程式以使其正常作業。我想到了什么：

• use fyne data binding: That should work for simple stuff such as the label text in the example above. But what if I have to update more in a very custom way according to a model's state. Say I'd have to update a button's enabled state based on a model's condition. How can this be bound to data? Is that possible at all?

• use interfaces as in the standard MVC design pattern: I tried this as well but couldn't really get my head around it. I created a separate module that would provide an interface which could then be imported by the model class. I would then register a view that (implicitly) implements that interface with the model. But I couldn't get it to work. I assume that my understanding of go interfaces isn't really sufficient at this point.

• short polling the model: that's just meh and certainly not what the developers of Go and/or fyne intended :-)

Can anyone please point me to an idiomatic solution for this problem? I'm probably missing something very, very basic here...

uj5u.com熱心網友回復：

回傳值

您可以回傳該值。

func DoTimeConsumingStuff() int {
    time.Sleep(1 * time.Second)
    counter  
    return counter
}

然后在按鈕單擊時生成一個匿名 goroutine，以便不阻塞 UI。

counterButton := widget.NewButton("Increment", func() {
    go func() {
        counter := model.DoTimeConsumingStuff(counterChan)
        UpdateCounterLabel(counter)
    }()      
})

打回來

您可以將該UpdateCounterLabel函式傳遞給您的模型函式，即回呼。

func DoTimeConsumingStuff(callback func(int)) {
    time.Sleep(1 * time.Second)
    counter  
    callback(counter)
}

counterButton := widget.NewButton("Increment", func() {
    go model.DoTimeConsumingStuff(UpdateCounterLabel)
})

渠道

也許您也可以將通道傳遞給您的模型函式。但是使用上述方法，這似乎不是必需的。潛在地，如果您有多個計數器值來。

func DoTimeConsumingStuff(counterChan chan int) {
    for i := 0; i < 10; i   {
        time.Sleep(1 * time.Second)
        counter  
        counterChan <- counter
    }
    close(counterChan)
}

然后在 GUI 中，您可以從通道接收，再次在 goroutine 中以不阻塞 UI。

counterButton := widget.NewButton("Increment", func() {
    go func() {
        counterChan := make(chan int)
        go model.DoTimeConsumingStuff(counterChan)
        for counter := range counterChan {
            UpdateCounterLabel(counter)
        }
    }()      
})

當然，您也可以再次使用在每次迭代時呼叫的回呼。

標籤：go model-view-controller circular-dependency fyne

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