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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

Vue.js

Jetpack Compose

React

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.

Vue.js

javascript

<template>
  <div>{{ displayString }}</div>
</template>

<script setup>
import { defineProps } from 'vue';

const props = defineProps({
  displayString: String
});
</script>

Jetpack Compose

kotlin

@Composable
fun MyComponent(
    displayString: String
) {
    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.

Vue.js

javascript

<template>
  <p v-if="condition">Condition is true</p>
  <p v-else>Condition is false</p>
</template>

<script setup>
import { defineProps } from 'vue';

const props = defineProps({
  condition: Boolean
});
</script>

Jetpack Compose

kotlin

@Composable
fun ConditionalComponent(condition: Boolean) {
    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.

Vue.js

javascript

<template>
  <intermediate-component :data="data" />
</template>

<script setup>
import { defineProps } from 'vue';
import IntermediateComponent from './IntermediateComponent.vue';

const props = defineProps({
  data: String
});
</script>

Jetpack Compose

kotlin

@Composable
fun Parent(data: String) {
    IntermediateComponent(data = data)
}

@Composable
fun IntermediateComponent(data: String) {
    ChildComponent(data = data)
}

@Composable
fun ChildComponent(data: String) {
    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.

Vue.js

javascript

<template>
  <button @click="setClicked">
    {{ clicked ? "Button clicked" : "Click me" }}
  </button>
</template>

<script setup>
import { ref } from 'vue';

const clicked = ref(false);

function setClicked() {
  clicked.value = true;
}
</script>

Jetpack Compose

kotlin

@Composable
fun ClickableComponent() {
    var clicked by remember { mutableStateOf(false) }

    Button(onClick = { clicked = true }) {
        Text(if (clicked) "Button clicked" else "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.

Vue.js

javascript

<template>
  <input
    type="text"
    v-model="text"
    placeholder="Enter text"
  />
</template>

<script setup>
import { ref } from 'vue';

const text = ref('');
</script>

Jetpack Compose

kotlin

@Composable
fun TextInputComponent() {
    var text by remember { mutableStateOf("") }

    TextField(
        value = text,
        onValueChange = { newText -> text = newText },
        label = { Text("Enter 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.

Vue.js

Vue.js 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.

Jetpack Compose

kotlin

@Composable
fun ExampleComponent() {
    Text("Hello, World!")
}

@Preview(showBackground = true)
@Composable
fun ExampleComponentPreview() {
    ExampleComponent()
}

Additionally, you can also use Showkase, an open source library by Airbnb that allows you to view themes preview functions in an auto-generated component browser that can be viewed on an Android device.

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.

Vue.js

javascript

<template>
  <ul>
    <li v-for="item in items" :key="item">
      {{ item }}
    </li>
  </ul>
</template>

<script setup>
import { defineProps } from 'vue';

const props = defineProps({
  items: Array
});
</script>

<!-- Usage -->
<list-component :items="['Item 1', 'Item 2', 'Item 3']"></list-component>

Jetpack Compose

kotlin

@Composable
fun ListComponent(items: List<String>) {
    LazyColumn {
        items(items) { item ->
            Text(item)
        }
    }
}

// Usage
val items = listOf("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.

Vue.js

javascript

<template>
  <ul>
    <li v-for="person in items" :key="person.id">
      Name: {{ person.name }}, Age: {{ person.age }}
    </li>
  </ul>
</template>

<script setup>
import { defineProps } from 'vue';

const props = defineProps({
  items: Array
});
</script>

<!-- Usage -->
<item-keys-example
  :items="[
    { name: 'John', age: 30, id: '1' },
    { name: 'Jane', age: 28, id: '2' },
    { name: 'Bob', age: 25, id: '3' }
  ]"
></item-keys-example>

Jetpack Compose

kotlin

data class Person(val name: String, val age: Int, val id: String)

@Composable
fun ItemKeysExample(items: List<Person>) {
    LazyColumn {
        items(items, key = { person -> person.id }) { person ->
            Text("Name: ${person.name}, Age: ${person.age}")
        }
    }
}

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.

Vue.js

javascript

// ParentComponent.vue
<template>
  <div>
    <slot name="header"></slot>
    <slot name="content"></slot>
  </div>
</template>

// ChildComponent.vue
<template>
  <p>Child Content</p>
</template>

// Usage
<parent-component>
  <template v-slot:header>
    <h1>Header</h1>
  </template>
  <template v-slot:content>
    <child />
  </template>
</parent-component>

Jetpack Compose

kotlin

@Composable
fun Parent(
    header: @Composable () -> Unit,
    content: @Composable () -> Unit
) {
    Column {
        header()
        content()
    }
}

// Usage
Parent(
    header = { Text("Header") },
    content = { Child() }
)

@Composable
fun Child() {
    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.

Vue.js

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

javascript

<template>
  <div :style="style">Hello, World!</div>
</template>

<script setup>
import { reactive } from 'vue';

const style = reactive({
  padding: '16px',
  backgroundColor: 'blue',
  color: 'white'
});
</script>

Jetpack Compose

kotlin

@Composable
fun ModifiersExample() {
    Text(
        "Hello, World!",
        modifier = Modifier
            .padding(16.dp)
            .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.

Vue.js

javascript

<template>
  <button @click="incrementCount">
    Count: {{ count }}
  </button>
</template>

<script setup>
import { ref } from 'vue';

const count = ref(0);

function incrementCount() {
  count.value++;
}
</script>

Jetpack Compose

kotlin

@Composable
fun Counter() {
    var count by remember { mutableStateOf(0) }

    Button(onClick = { count = 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.

Vue.js

javascript

<!-- ParentComponent.vue -->
<template>
  <intermediate />
</template>

<script setup>
import { provide, ref } from 'vue';
import Intermediate from './IntermediateComponent.vue';

const data = ref('Some data');
provide('dataKey', data);
</script>

<!-- IntermediateComponent.vue -->
<template>
  <child />
</template>

<script setup>
import Child from './ChildComponent.vue';
</script>

<!-- ChildComponent.vue -->
<template>
  <p>Received data: {{ data }}</p>
</template>

<script setup>
import { inject } from 'vue';

const data = inject('dataKey');
</script>


<!-- Usage -->
<parent-component data="Some data"></parent-component>

Jetpack Compose

kotlin

val CustomLocal = compositionLocalOf<String> { "Default data" }

@Composable
fun Parent(data: String) {
    CompositionLocalProvider(CustomLocal provides data) {
        Intermediate()
    }
}

@Composable
fun Intermediate() {
    Child()
}

@Composable
fun Child() {
    val data = CustomLocal.current
    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.

Vue.js

javascript

<template>
  <div></div>
</template>

<script setup>
import { onMounted } from 'vue';

onMounted(() => {
  // Perform side effect here
});
</script>

Jetpack Compose

kotlin

@Composable
fun SideEffectOnLoadComponent() {
    LaunchedEffect(Unit) {
        // Perform side effect, e.g. fetch data, update external data source
    }

    // 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 />;
}

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