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:

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:

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}
     
    />
  );
};

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:

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

View Violations

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 />;

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

Reference Documentation

For detailed examples and edge cases, read:

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