container-view-pattern

Container/View Pattern

This skill provides guidance and validation for the Container/View component pattern used in this codebase.

Pattern Overview

The Container/View pattern separates components into two distinct files:

• Container (*Container.tsx): Handles logic, state, API calls, data fetching, and event handlers
• View (*View.tsx): Handles rendering UI only, receiving all data and callbacks as props
• Index (index.tsx): Exports the Container as the default component

Where This Pattern Applies

The Container/View pattern is required in these directories:

Directory	Applies	Notes
features/*/components/	Yes	All feature components
features/*/screens/	Yes	All feature screens
components/	Yes	Shared components
screens/	Yes	Shared screens
components/ui/	No	UI primitives (GlueStack)
components/shared/	No	Simple shared utilities
components/icons/	No	Icon components

When to Use This Skill

• Creating a new component in any of the directories above
• Validating that existing components follow the pattern
• Refactoring a component to follow the pattern
• Reviewing code for pattern compliance

Creating a New Component

Option 1: Use the Skill Generator Script

Run the skill's generator script for any component type:

python3 .claude/skills/container-view-pattern/scripts/create_component.py <type> <name> [feature]

Component Types:

Type	Command	Creates in
Global component	create_component.py global-component PlayerCard	components/PlayerCard/
Feature component	create_component.py feature-component PlayerCard player-kanban	features/player-kanban/components/PlayerCard/
Global screen	create_component.py global-screen Settings	screens/Settings/
Feature screen	create_component.py feature-screen Main dashboard	features/dashboard/screens/Main/

Option 2: Manual Creation

Create the following directory structure:

ComponentName/
├── ComponentNameContainer.tsx
├── ComponentNameView.tsx
└── index.tsx

Container Component Requirements

Container components handle all business logic:

1. Single View render: Container must ONLY render its corresponding View component - no other UI elements or components
2. State management: Use useState, useReducer
3. Data fetching: Use GraphQL hooks, API calls
4. Memoization: Wrap all computed values in useMemo
5. Event handlers: Wrap all handlers in useCallback with proper dependencies
6. Formatting: All data transformation and formatting logic
7. Conditional logic: Determine what state to pass to View (loading, error, empty flags)

Container Code Order (enforced by ESLint)

Containers must follow this specific order:

const ExampleContainer = () => {
  // 1. Variables, state, useMemo, useCallback (same group)
  const [state, setState] = useState();
  const computed = useMemo(() => state * 2, [state]);
  const handleClick = useCallback(() => {}, []);

  // 2. useEffect hooks
  useEffect(() => {
    // side effects
  }, []);

  // 3. Return statement (always last)
  return <ExampleView />;
};

Container Template

import { useCallback, useMemo, useState } from "react";
import ComponentNameView from "./ComponentNameView";

/**
 * Props for the ComponentName component.
 */
interface ComponentNameProps {
  readonly id: string;
}

/**
 * Container component that manages state and logic for ComponentName.
 * @param props - Component properties
 * @param props.id - The unique identifier
 */
const ComponentNameContainer = ({ id }: ComponentNameProps) => {
  // State
  const [isLoading, setIsLoading] = useState(false);

  // Memoized computed values
  const formattedData = useMemo(() => {
    return data?.toUpperCase() ?? "";
  }, [data]);

  // Event handlers wrapped in useCallback
  const handleSubmit = useCallback(() => {
    setIsLoading(true);
  }, []);

  return (
    <ComponentNameView
      formattedData={formattedData}
      isLoading={isLoading}
      onSubmit={handleSubmit}
    />
  );
};

export default ComponentNameContainer;

View Component Requirements

View components are pure presentation:

1. Arrow function shorthand: Use () => (...) not () => { return (...); }
2. No return statements: The component body must be a single JSX expression
3. memo wrapper: Export with memo() for performance optimization
4. displayName: Set ComponentName.displayName = "ComponentName"
5. Readonly props: All props should be marked as readonly
6. No hooks: View should not contain useState, useEffect, useMemo, etc.
7. No logic: All conditional rendering should use ternary expressions in JSX

View Template

import { memo } from "react";

import { Box } from "@/components/ui/box";
import { Text } from "@/components/ui/text";

/**
 * Props for the ComponentNameView component.
 */
interface ComponentNameViewProps {
  readonly formattedData: string;
  readonly isLoading: boolean;
  readonly onSubmit: () => void;
}

/**
 * View component that renders the ComponentName UI.
 * @param props - Component properties
 * @param props.formattedData - Pre-formatted display data
 * @param props.isLoading - Loading state indicator
 * @param props.onSubmit - Submit handler callback
 */
const ComponentNameView = ({
  formattedData,
  isLoading,
  onSubmit,
}: ComponentNameViewProps) => (
  <Box testID="COMPONENT_NAME.CONTAINER">
    {isLoading ? <Text>Loading...</Text> : <Text>{formattedData}</Text>}
  </Box>
);

ComponentNameView.displayName = "ComponentNameView";

export default memo(ComponentNameView);

Index File

Export the Container as the default:

export { default } from "./ComponentNameContainer";

Validation

ESLint Rules

The following ESLint rules enforce the pattern:

Rule	Description
component-structure/enforce-component-structure	Validates directory structure and file naming
component-structure/no-return-in-view	Ensures View uses arrow shorthand
component-structure/require-memo-in-view	Ensures View uses memo and displayName
component-structure/single-component-per-file	One component per file

Manual Validation

Run the validation script to check a component:

python3 .claude/skills/container-view-pattern/scripts/validate_component.py <path-to-component-directory>

Run ESLint to check all components:

bun run lint

Note: Replace bun with your project's package manager (npm, yarn, pnpm) as needed.

Common Violations

Container Violations

Issue	Resolution
Rendering UI elements besides View	Container must ONLY return the corresponding View component
Rendering multiple components	Move all UI to View; Container returns only View
Missing useMemo for objects/arrays	Wrap computed values in useMemo
Missing useCallback for functions	Wrap handlers in useCallback
Logic in View component	Move logic to Container
Inline function props	Create memoized handler

View Violations

Issue	Resolution
Using block body { return }	Convert to arrow shorthand () => (...)
Missing memo wrapper	Add export default memo(ComponentView)
Missing displayName	Add ComponentView.displayName = "ComponentView"
Contains hooks	Move hooks to Container
Contains state	Move state to Container

Extracting Helper Functions

When View components exceed ESLint's cognitive complexity threshold (28), extract render helper functions. For simple cases, prefer inline JSX:

/**
 * Renders the loading skeleton state.
 * @param props - Helper function properties
 * @param props.isDark - Whether dark mode is active
 */
function renderLoadingState(props: { readonly isDark: boolean }) {
  const { isDark } = props;
  return <LoadingSkeleton isDark={isDark} />;
}

const ComponentView = ({ isLoading, isDark }: Props) => (
  <Box>{isLoading ? renderLoadingState({ isDark }) : <Content />}</Box>
);

Event Handler Naming Convention

• Container: Use handle* prefix (e.g., handleSubmit, handleClick)
• View props: Use on* prefix (e.g., onSubmit, onClick)

// Container
const handleSubmit = useCallback(() => { ... }, []);
return <ComponentView onSubmit={handleSubmit} />;

// View
const ComponentView = ({ onSubmit }: Props) => (
  <Button onPress={onSubmit}>Submit</Button>
);

Reference Documentation

For detailed examples and edge cases, read:

• references/patterns.md - Common patterns and anti-patterns
• references/examples.md - Complete component examples