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Compare Declarative Frameworks

Choose up-to 3 frameworks and learn how they compare to each other.
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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)
    }
}
React
jsx
function MyComponent(props) {
  return <div>{props.displayString}</div>;
}
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)
React
jsx
function ConditionalComponent({ condition }) {
  return (
    <>
      {condition ? (
        <p>Condition is true</p>
      ) : (
        <p>Condition is false</p>
      )}
    </>
  );
}

// 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")
React
jsx
function Parent({ data }) {
  return <IntermediateComponent data={data} />;
}

function IntermediateComponent({ data }) {
  return <ChildComponent data={data} />;
}

function ChildComponent({ data }) {
  return <p>Received data: {data}</p>;
}

// 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")
        }
    }
}
React
jsx
import { useState } from "react";

function ClickableComponent() {
  const [clicked, setClicked] = useState(false);

  return (
    <button onClick={() => setClicked(true)}>
      {clicked ? "Button clicked" : "Click me"}
    </button>
  );
}
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)
    }
}
React
jsx
function TextInputComponent() {
  const [text, setText] = useState("");

  return (
    <input
      type="text"
      value={text}
      onChange={(e) => setText(e.target.value)}
      placeholder="Enter 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()
    }
}
React

React doesn't have a built-in preview feature. However, you can use a tool like Storybook to create previews for your components in a separate development environment.

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)
React
jsx
function ListComponent({ items }) {
  return (
    <ul>
      {items.map((item) => (
        <li key={item}>{item}</li>
      ))}
    </ul>
  );
}

// Usage
const 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")])
React
jsx
function ItemKeysExample({ items }) {
  return (
    <ul>
      {items.map((person) => (
        <li key={person.id}>
          Name: {person.name}, Age: {person.age}
        </li>
      ))}
    </ul>
  );
}

// Usage
<ItemKeysExample
  items={[
    { name: "John", age: 30, id: "1" },
    { name: "Jane", age: 28, id: "2" },
    { 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")
    }
}
React
jsx
function Parent({ header, content }) {
  return (
    <div>
      {header}
      {content}
    </div>
  );
}

// Usage
<Parent header={<h1>Header</h1>} content={<Child />} />;

function Child() {
  return <p>Child Content</p>;
}
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)
    }
}
React

React doesn't have a direct analog to modifiers in Jetpack Compose or SwiftUI. Instead, you can use inline styles or CSS classes.

jsx
function ModifiersExample() {
  const style = {
    padding: "16px",
    backgroundColor: "blue",
    color: "white",
  };

  return <div style={style}>Hello, World!</div>;
}
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)")
        }
    }
}
React
jsx
import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <button onClick={() => setCount(count + 1)}>
        Count: {count}
    </button>
  );
}
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")
React
jsx
import { createContext, useContext } from "react";

const CustomContext = createContext();

function Parent({ data }) {
  return (
    <CustomContext.Provider value={data}>
      <Intermediate />
    </CustomContext.Provider>
  );
}

function Intermediate() {
  return <Child />;
}

function Child() {
  const data = useContext(CustomContext);
  return <p>Received data: {data}</p>;
}

// 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!")
    }
}
React
jsx
import { useEffect } from "react";

function SideEffectOnLoadComponent() {
  useEffect(() => {
    // Perform side effect, e.g. fetch data, update external data source
  }, []);

  // Other UI components
  return <div />;
}