How can I infer generic parameter in extension? - swift

Question

I have a very simple CustomView which it takes a View and modify it! Like this code:
struct CustomView<ViewType: View>: View {
let content: () -> ViewType
var body: some View {
return content()
.foregroundColor(.red)
}
}
So far so good!
Now I want make a CustomModifier out of it, like this:
extension View {
func customModifier<ViewModifierType: View>(viewModifier: () -> ViewModifierType) -> some View {
// how can I import self from here?
return viewModifier()
}
}
use case:
struct ContentView: View {
var body: some View {
Text("Hello, World!")
.customModifier(viewModifier: { CustomView(content: { Text("Hello, World!") } ) }) // <<: Here is the issue!
// How can I satisfy CustomView with self in extension? that could help to cut Text("Hello, World!") to feeding as content for CustomView?
}
}
So if see the codes, all I am trying to do is cut off Text("Hello, World!") with using self from extension and trying to have this form of coding:
.customModifier(viewModifier: { CustomView() })
PS: I know that for having form of CustomView() I have to respect the generic parameter CustomView with word of where but I do not know how can I put these all puzzle together!

Answer 1

If I understand you correctly, then try this
extension View {
func customModifier<ViewModifierType: View>(viewModifier: (Self) -> ViewModifierType) -> some View {
return viewModifier(self)
}
}

Answer 2

Not sure what is your goal but if you just want to add a red foreground to a view you need to implement a view modifier:
struct RedForeground: ViewModifier {
func body(content: Content) -> some View {
content.foregroundColor(.red)
}
}
And then just call it using the modifier method:
Text("Text")
.modifier(RedForeground())
If you want to simplify it further you can extend View and add make it a computed property:
extension View {
var redForeground: some View { modifier(RedForeground()) }
}
usage:
Text("Text")
.redForeground

Answer 3

You can't just init CustomView without a view, but you can pass CustomView initializer as function to customModifier, like this:
struct ContentView: View {
var body: some View {
Text("Hello, World!")
.customModifier(viewModifier: CustomView.init)
}
}
struct CustomView<ViewType: View>: View {
let content: ViewType
var body: some View {
return content
.foregroundColor(.red)
}
}
extension View {
func customModifier<ViewModifierType: View>(viewModifier: (Self) -> ViewModifierType) -> some View {
return viewModifier(self)
}
}