ScrollViewLoader

A simple utility to assist with loading more content in a ScrollView in SwiftUI.

Usage

Add .shouldLoadMore to any ScrollView. By default it will be triggered when the content at the bottom of the ScrollView is close to being in view.

See it in action

If you want to see it in a real app, check out dateit

Also works well with SwiftUI-Refresher

Usage

First add the package to your project.

import ScrollViewLoader

struct ContentView: View {
    
    @State var data: [Int] = Array(0..<1)
    
    var body: some View {
        ScrollView {
            LazyVStack {
                ForEach(data, id: \.self) { i in
                    Text("\(i)")
                        .font(.title)
                        .frame(maxWidth: .infinity)
                }
                ProgressView()
                    .scaleEffect(2)
            }
        }
        .shouldLoadMore {
            await Task.sleep(seconds: 0.05)
            data.append(data.last! + 1)
        }
    }
}

Customization

By default, the callback will be triggered when distance to the bottom of the scrollable content is less than 50% of the visible hight of the scroll view. You can customize this

Set the relative offset to 20% instead of the default 50%:

.shouldLoadMore(bottomDistance: .relative(0.2)) { 
    // Load more
}

Set the absolute offset to a fixed value:

.shouldLoadMore(bottomDistance: .absolute(200)) { 
    // Load more
}

`waitForHeightChange`

It may be desirable for shouldLoadMore to be called whenever the user scrolls - even if the scroll view content didn't change. You can change this behavior with waitForHeightChange:

.shouldLoadMore(waitForHeightChange: .never) { 
    // Will be called regardless of if the content height changed from a previous update
}

.shouldLoadMore(waitForHeightChange: .always) { 
    // Will only be called if the content height changed since last time
}

.shouldLoadMore(waitForHeightChange: .until(2)) { 
    // Will only be called if the content height changed since last time or after 2 seconds of no change
}

By default waitForHeightChange is .until(2) so the function doesn't get called in quick succession when no content updates are made.

More details

The callback will only be called once when the bottom approaches.
If you scroll back up out of the trigger zone, it will be called again when you scroll back down.
It is up to you to synchronize and de-duplicate multiple scroll triggers by the user (depending on the kind of data you are loading)
Loading conditions will be re-evaluated if the scroll view content changes in any way.

More Examples

Using a completion handler instead of `async`

.shouldLoadMore { done in
    loadYourContent {
        data.append(data.last! + 1)
        done() // Call done so shouldLoadMore can be called again later
    }
}

Larger batching