State Management in SwiftUI - SwiftUI Basic Tutorial - Ep 4

[00:00:00]Hi everyone.

[00:00:01]In this video, we are going to see state management in Swift UI.

[00:00:06]First, we will see state variable.

[00:00:09]Whenever state variable changes, Swift UI automatically refreshes the UI.

[00:00:15]Let's see an example.

[00:00:18]I have already created a project.

[00:00:22]Now, I'm going to modify the content view.

[00:00:28]In this sample, I'm going to create and small example where uh it has some count count button, and whenever the increase button is clicked, the text view will be updated.

[00:00:49]I'm including the V stack and text view.

[00:00:59]And a button.

[00:01:08]Naming the button as uh in- increment count.

[00:01:21]And include a state variable.

[00:01:36]In the text view, I'm including the state variable count.

[00:01:50]In the button action, I am in- incrementing the count.

[00:02:03]So, now I'm going to give the spacing in the V stack.

[00:02:14]So, you can see in the preview it has one button and text view.

[00:02:22]Whenever I'm going to click the uh button, it will increment the count value. So, I'm going to click the button.

[00:02:30]You can see it increased to one.

[00:02:34]And again clicking it, it increased to two. So, whenever the state variable changes, the text view will be updated as it is using the state variable.

[00:02:48]Now, we are going to see another scenario.

[00:02:52]Suppose, this button is in the child view.

[00:02:57]In that case, how we can manage?

[00:03:00]So, I'm going I'm going to create a child view.

[00:03:23]I'm in I'm copy pasting to child view.

[00:03:27]And now we are going to pass count to the child view. For that, we have to include binding.

[00:03:48]Now, include the child view in the parent.

[00:03:54]Okay. To pass the To pass value to the binding, we have to include dollar symbol.

[00:04:03]Okay.

[00:04:04]Now, I'm going to click the button and value will be increased.

[00:04:14]Next, we are going to see state object and observed object.

[00:04:19]Suppose, this count value is in the model. In that case, how we can manage?

[00:04:28]I'm going to create a class.

[00:04:31]Name it as counter model.

[00:04:36]And where count and it will be zero.

[00:04:50]Suppose, value is in the is in the this uh counter model.

[00:04:55]In this case In this case, how we can manage is we can use state object.

[00:05:02]For that, we have to extend counter model into observable object.

[00:05:13]And we have to mention count as published.

[00:05:21]For including the observable object, we have to import combine.

[00:05:34]To initialize model, we have to make the model as state object.

[00:05:47]Counter model.

[00:06:05]First we will do in the parent view itself.

[00:06:09]Next we will go for child view.

[00:06:16]I'm including the button in the parent view itself.

[00:06:20]So, So, when I'm in clicking the button, the text will be increased.

[00:06:51]Here, whenever the published variable in the model is updated, the view which is using the variable will be updated.

[00:07:05]Next, we will include the button in the child view.

[00:07:16]So, I'm I'm including in the child view.

[00:07:24]So, to pass the state object into the child view, we have to include observed object.

[00:07:50]>> We can pass the model into the child view.

[00:07:54]Now, we can uh see the output in the preview. So, I'm clicking the button.

[00:08:01]We can see text view is increased.

[00:08:05]Next, we are going to see environment object supports We have to pass model into the uh from parent to child when there is multiple level of uh uh parent-child uh views, then we can use environment object.

[00:08:29]Here, in the child view we have to mention environment object and we no need to pass in the parameter.

[00:08:47]You have to assign in the V stacks environment object.

[00:09:03]So, now we can check the preview.

[00:09:07]I'm clicking the button.

[00:09:09]So, text view is increased.

[00:09:12]So, in this case we can uh use the environment object.

[00:09:17]Thanks for watching this video.