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JetpackCompose.app's Newsletter

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JetpackCompose.app's Newsletter

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Thanks for taking the time and energy to do it so well

Compare Declarative Frameworks

Choose up-to 3 frameworks and learn how they compare to each other.

Jetpack Compose

SwiftUI

Flutter

React

Vue.js

Concept

SwiftUI

Creating a new Component

Components are the reusable building blocks of your application. They are the most basic UI elements and can be used to build more complex components.

SwiftUI

swift

struct MyComponent: View {
    var displayString: String
    var body: some View {
        Text(displayString)
    }
}

Conditional Rendering

Conditional rendering is a technique used to display different UI components or content based on certain conditions, such as the value of a variable or the outcome of a boolean expression.

SwiftUI

swift

struct ConditionalComponent: View {
    let condition: Bool

    var body: some View {
        Group {
            if condition {
                Text("Condition is true")
            } else {
                Text("Condition is false")
            }
        }
    }
}

// Usage
ConditionalComponent(condition: true)

Prop/Parameter Drilling

Prop/Parameter drilling is a technique where data is passed through multiple layers of components in the component hierarchy, often from a parent component to a deeply nested child component, via props or parameters.

SwiftUI

swift

struct Parent: View {
    let data: String

    var body: some View {
        IntermediateComponent(data: data)
    }
}

struct IntermediateComponent: View {
    let data: String

    var body: some View {
        ChildComponent(data: data)
    }
}

struct ChildComponent: View {
    let data: String

    var body: some View {
        Text("Received data: \(data)")
    }
}

// Usage
Parent(data: "Some data")

Responding to events

Responding to events involves handling user interactions, such as button clicks or text input changes, and updating the component's state or triggering side effects accordingly.

SwiftUI

swift

struct ClickableComponent: View {
    @State private var clicked = false

    var body: some View {
        Button(action: {
            clicked = true
        }) {
            Text(clicked ? "Button clicked" : "Click me")
        }
    }
}

Handing user input

Handling user input involves capturing and processing user interactions with input fields, such as text fields, sliders, or checkboxes, and updating the component's state or triggering side effects based on the input.

SwiftUI

swift

struct TextInputComponent: View {
    @State private var text = ""

    var body: some View {
        TextField("Enter text", text: $text)
    }
}

Previewing a Component

Creating a preview of a component involves displaying a visual representation of the component in the development environment to help with the design and layout process.

SwiftUI

swift

struct ExampleComponent: View {
    var body: some View {
        Text("Hello, World!")
    }
}

struct ExampleComponent_Previews: PreviewProvider {
    static var previews: some View {
        ExampleComponent()
    }
}

Lists & Looping

Lists and looping involve rendering a dynamic number of components based on the length of a list or array, iterating over the list, and generating a UI component for each item.

SwiftUI

swift

struct ListComponent: View {
    let items: [String]

    var body: some View {
        List(items, id: \.self) { item in
            Text(item)
        }
    }
}

// Usage
let items = ["Item 1", "Item 2", "Item 3"]
ListComponent(items: items)

List item keys

List Item Keys are unique identifiers assigned to each list item in declarative UI frameworks to help manage and update list elements efficiently. Using List Item Keys enables the framework to optimize the rendering process, minimizing unnecessary updates and improving overall performance.

SwiftUI

swift

struct Person: Identifiable {
    let name: String
    let age: Int
    let id: String
}

struct ItemKeysExample: View {
    let items: [Person]

    var body: some View {
        List(items) { person in
            Text("Name: \(person.name), Age: \(person.age)")
        }
    }
}

// Usage
ItemKeysExample(items: [Person(name: "John", age: 30, id: "1"), Person(name: "Jane", age: 28, id: "2"), Person(name: "Bob", age: 25, id: "3")])

Slot APIs

Slot APIs refer to a technique where components have customizable parts or 'slots' that can be filled with content when the component is being used. This allows for greater reusability and flexibility in composing user interfaces. The content that fills these slots can be other components or simple UI elements like text or images.

SwiftUI

swift

struct Parent<Header: View, Content: View>: View {
    let header: Header
    let content: Content

    var body: some View {
        VStack {
            header
            content
        }
    }
}

// Usage
Parent(
    header: Text("Header"),
    content: Child()
)

struct Child: View {
    var body: some View {
        Text("Child Content")
    }
}

Modifiers

Modifiers are used to adjust or configure the UI elements' appearance or behavior in a declarative UI framework.

SwiftUI

swift

struct ModifiersExample: View {
    var body: some View {
        Text("Hello, World!")
            .padding(EdgeInsets(top: 16, leading: 16, bottom: 16, trailing: 16))
            .background(Color.blue)
    }
}

State

State management refers to the process of handling and updating the internal state of components, often in response to user interactions or other events.

SwiftUI

swift

struct Counter: View {
    @State private var count = 0

    var body: some View {
        Button(action: {
            count += 1
        }) {
            Text("Count: \(count)")
        }
    }
}

Scoped Data Propagation

Scoped Data Propagation is a technique that involves passing data across multiple levels of a component subtree without having to explicitly pass it through every intermediate component. It helps reduce the complexity of prop drilling and allows for a more efficient way of sharing data in a specific scope.

SwiftUI

swift

struct CustomEnvironmentKey: EnvironmentKey {
    static let defaultValue: String = ""
}

extension EnvironmentValues {
    var customData: String {
        get { self[CustomEnvironmentKey.self] }
        set { self[CustomEnvironmentKey.self] = newValue }
    }
}

struct Parent: View {
    let data: String

    var body: some View {
        Intermediate().environment(\.customData, data)
    }
}

struct Intermediate: View {
    var body: some View {
        Child()
    }
}

struct Child: View {
    @Environment(\.customData) private var data

    var body: some View {
        Text("Received data: \(data)")
    }
}

// Usage
Parent(data: "Some data")

Side Effects

A side effect involves executing code that can have external consequences or perform operations that are not directly related to rendering the UI, such as making network requests or updating external data sources.

SwiftUI

swift

struct SideEffectOnLoadComponent: View {
    @State private var hasPerformedSideEffect = false

    var body: some View {
        if !hasPerformedSideEffect {
            DispatchQueue.main.async {
                // Perform side effect, e.g. fetch data, update external data source
                hasPerformedSideEffect = true
            }
        }

        // Other UI components
        Text("Hello, World!")
    }
}

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