65 lines
1.9 KiB
Markdown
65 lines
1.9 KiB
Markdown
# Creating Widgets
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Widgets are special views that do not provide a collection of other views as a content,
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but have functions that are called when creating or updating the view.
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Normally, a widget manages a GTK or Libadwaita widget using [SwiftGui][1].
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## Recreate the `Text` widget
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In this tutorial, we will recreate the text widget.
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A widget conforms to the `Widget` protocol:
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```swift
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struct CustomText: Widget { }
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```
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You can add properties to the widget:
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```swift
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struct CustomText: Widget {
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var text: String
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}
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```
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This widget can be called in a view body using `CustomText(text: "Hello, world!")`.
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Now, add the two functions required by the protocol:
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```swift
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struct CustomText: Widget {
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var text: String
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public func container() -> ViewStorage { }
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public func update(_ storage: ViewStorage) { }
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}
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```
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## The `container()` Function
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This function initializes the widget when the widget appears for the first time.
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It expects a `ViewStorage` as the return type.
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In our case, this function is very simple:
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```swift
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func container() -> ViewStorage {
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.init(MarkupLabel(self.text))
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}
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```
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`MarkupLabel` is defined in [SwiftGui][1].
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## The `update(_:)` Function
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Whenever a state of the app changes, the `update(_:)` function of the widget gets called.
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You get the view storage that you have previously initialized as a parameter.
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Update the storage to reflect the current state of the widget:
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```swift
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func update(_ storage: ViewStorage) {
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if let label = storage.view as? MarkupLabel {
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label.setText(text)
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}
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}
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```
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## Containers
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Some widgets act as containers that accept other widgets as children.
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In that case, use the `ViewStorage`'s `content` property for storing their view storages.
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In the `update(_:)` function, update the children's storages.
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An example showcasing how to implement containers is the [VStack][2].
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[1]: https://github.com/JCWasmx86/SwiftGui
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[2]: ../../Sources/Adwaita/View/VStack.swift
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