Your First Workflow Builder App

This is a comprehensive tutorial for building a complete visual workflow application with React. For a quick 5-minute intro, see Visual Builder Quick Start.

In this tutorial, you’ll build a fully-featured workflow builder application with:

Multiple custom nodes (input, math, display)
Visual drag-and-drop interface
Property editing panel
Save/load functionality
Execution with progress feedback
Error handling

Time Required: 30-45 minutes

What We’ll Build

A calculator workflow app where users can:

Add number input nodes and set values
Drag math operation nodes (add, multiply, subtract)
Connect nodes visually
Execute the workflow and see results
Save/load workflows as JSON

Prerequisites

Node.js 18+ installed
Basic React knowledge
Familiarity with TypeScript

Step 1: Create React Project

We’ll use Vite for fast development:

npm create vite@latest my-workflow-app -- --template react-ts
cd my-workflow-app
npm install

Step 2: Install CrystalFlow

npm install @crystalflow/react @crystalflow/core @crystalflow/types reflect-metadata
npm install reactflow

Step 3: Configure TypeScript

Update tsconfig.json to enable decorators:

tsconfig.json

{
  "compilerOptions": {
    "target": "ES2020",
    "useDefineForClassFields": true,
    "lib": ["ES2020", "DOM", "DOM.Iterable"],
    "module": "ESNext",
    "skipLibCheck": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    
    /* Bundler mode */
    "moduleResolution": "bundler",
    "allowImportingTsExtensions": true,
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true,
    "jsx": "react-jsx",

    /* Linting */
    "strict": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noFallthroughCasesInSwitch": true
  },
  "include": ["src"],
  "references": [{ "path": "./tsconfig.node.json" }]
}

Step 4: Create Custom Nodes

Create a src/nodes directory for your workflow nodes.

Number Input Node

src/nodes/NumberInputNode.ts

import 'reflect-metadata';
import { Node, defineNode, Property, Output } from '@crystalflow/core';

@defineNode({
  type: 'input.number',
  label: 'Number Input',
  category: 'Input',
  description: 'Provides a number value'
})
export class NumberInputNode extends Node {
  @Property({
    type: 'number',
    label: 'Value',
    defaultValue: 0,
    step: 1
  })
  value: number = 0;

  @Output({ type: 'number', label: 'Value' })
  output: number;

  execute() {
    this.output = this.value;
  }
}

Math Nodes

src/nodes/MathNodes.ts

import { Node, defineNode, Input, Output } from '@crystalflow/core';

@defineNode({
  type: 'math.add',
  label: 'Add',
  category: 'Math',
  description: 'Add two numbers'
})
export class AddNode extends Node {
  @Input({ type: 'number', label: 'A' })
  a: number = 0;

  @Input({ type: 'number', label: 'B' })
  b: number = 0;

  @Output({ type: 'number', label: 'Result' })
  result: number;

  execute() {
    this.result = this.a + this.b;
  }
}

  category: 'Math',
  description: 'Multiply two numbers'
})
export class MultiplyNode extends Node {
  @Input({ type: 'number', label: 'A' })
  a: number = 1;

  @Input({ type: 'number', label: 'B' })
  b: number = 1;

  @Output({ type: 'number', label: 'Result' })
  result: number;

  execute() {
    this.result = this.a * this.b;
  }
}

@defineNode({
  type: 'math.subtract',
  label: 'Subtract',
  category: 'Math',
  description: 'Subtract B from A'
})
export class SubtractNode extends Node {
  @Input({ type: 'number', label: 'A' })
  a: number = 0;

  @Input({ type: 'number', label: 'B' })
  b: number = 0;

  @Output({ type: 'number', label: 'Result' })
  result: number;

  execute() {
    this.result = this.a - this.b;
  }
}

Display Node

src/nodes/DisplayNode.ts

import { Node, defineNode, Input } from '@crystalflow/core';

@defineNode({
  type: 'output.display',
  label: 'Display',
  category: 'Output',
  description: 'Display a value'
})
export class DisplayNode extends Node {
  @Input({ type: 'any', label: 'Value' })
  value: any = null;

  execute() {
    console.log('📊 Result:', this.value);
  }
}

Export All Nodes

src/nodes/index.ts

export { NumberInputNode } from './NumberInputNode';
export { AddNode, MultiplyNode, SubtractNode } from './MathNodes';
export { DisplayNode } from './DisplayNode';

Step 5: Create the Main App Component

Now let’s create the React component that uses CrystalFlow’s visual builder:

src/App.tsx

import React, { useState } from 'react';
import 'reflect-metadata';
import { WorkflowBuilder } from '@crystalflow/react';
import { ExecutionResult } from '@crystalflow/core';
import {
  NumberInputNode,
  AddNode,
  MultiplyNode,
  SubtractNode,
  DisplayNode
} from './nodes';
import 'reactflow/dist/style.css';
import './App.css';

function App() {
  const [executionResult, setExecutionResult] = useState<ExecutionResult | null>(null);
  const [error, setError] = useState<Error | null>(null);

  // Define available nodes
  const nodes = [
    NumberInputNode,
    AddNode,
    MultiplyNode,
    SubtractNode,
    DisplayNode
  ];

  const handleExecute = (result: ExecutionResult) => {
    console.log('Workflow executed:', result);
    setExecutionResult(result);
    setError(null);

    if (result.status === 'success') {
      console.log('✅ Success! Duration:', result.duration, 'ms');
    } else if (result.error) {
      console.error('❌ Execution failed:', result.error);
      setError(result.error);
    }
  };

  const handleError = (err: Error) => {
    console.error('Error:', err);
    setError(err);
  };

  return (
    <div className="app">
      <header className="app-header">
        <h1>🎯 Workflow Calculator</h1>
        <p>Build workflows visually - drag, connect, and execute!</p>
      </header>

      <div className="workflow-container">
        <WorkflowBuilder
          nodes={nodes}
          onExecute={handleExecute}
          onError={handleError}
          showNodePalette={true}
          showPropertyPanel={true}
          showToolbar={true}
        />
      </div>

      {executionResult && (
        <div className="results-panel">
          <h3>Execution Result</h3>
          <div className="result-status">
            Status: <span className={`status-${executionResult.status}`}>
              {executionResult.status}
            </span>
          </div>
          <div className="result-duration">
            Duration: {executionResult.duration}ms
          </div>
          {error && (
            <div className="result-error">
              Error: {error.message}
            </div>
          )}
        </div>
      )}
    </div>
  );
}

export default App;

Step 6: Add Styling

Create src/App.css:

src/App.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
}

.app-header {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 1.5rem 2rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.app-header h1 {
  font-size: 1.8rem;
  margin-bottom: 0.5rem;
}

.app-header p {
  opacity: 0.9;
  font-size: 0.95rem;
}

.workflow-container {
  flex: 1;
  position: relative;
  background: #f5f7fa;
}

.results-panel {
  background: white;
  border-top: 2px solid #e5e7eb;
  padding: 1rem 2rem;
  box-shadow: 0 -2px 8px rgba(0,0,0,0.05);
}

.results-panel h3 {
  margin-bottom: 0.75rem;
  color: #374151;
}

.result-status {
  margin: 0.5rem 0;
  font-weight: 500;
}

.status-success {
  color: #10b981;
}

.status-failed {
  color: #ef4444;
}

.status-cancelled {
  color: #f59e0b;
}

.result-duration {
  color: #6b7280;
  font-size: 0.9rem;
}

.result-error {
  margin-top: 0.5rem;
  padding: 0.75rem;
  background: #fef2f2;
  border-left: 3px solid #ef4444;
  color: #991b1b;
  border-radius: 4px;
}

Step 7: Update Main Entry Point

Update src/main.tsx:

src/main.tsx

import React from 'react';
import ReactDOM from 'react-dom/client';
import App from './App';
import './index.css';

ReactDOM.createRoot(document.getElementById('root')!).render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
);

Step 8: Run Your App

npm run dev

Open http://localhost:5173 in your browser!

Using Your Workflow Builder

Add Nodes

Drag nodes from the left palette onto the canvas. Try adding:

Two Number Input nodes
One Add node
One Display node

Set Values

Click a Number Input node to select it. In the right property panel, set its value (e.g., 5 and 3).

Connect Nodes

Drag from the output handle (right side, blue dot) of Number Input to the input handle (left side) of the Add node. Connect both inputs.

Connect Display

Connect the Add node’s Result output to the Display node’s Value input.

Execute

Click the ▶️ Execute button in the toolbar. Check the console and results panel!

Adding Features

Save and Load Workflows

Add save/load handlers:

const handleWorkflowChange = (workflow: Workflow) => {
  // Auto-save to localStorage
  localStorage.setItem('workflow', JSON.stringify(workflow.toJSON()));
};

// Load on mount
useEffect(() => {
  const saved = localStorage.getItem('workflow');
  if (saved) {
    const workflowData = JSON.parse(saved);
    setInitialWorkflow(Workflow.fromJSON(workflowData));
  }
}, []);

<WorkflowBuilder
  initialWorkflow={initialWorkflow}
  onWorkflowChange={handleWorkflowChange}
  // ... other props
/>

Add Progress Tracking

const [isExecuting, setIsExecuting] = useState(false);
const [progress, setProgress] = useState(0);

const handleExecute = (result: ExecutionResult) => {
  setIsExecuting(false);
  setProgress(100);
  // ... rest of handler
};

// Show progress during execution
{isExecuting && (
  <div className="progress-bar">
    <div className="progress" style={{ width: `${progress}%` }} />
  </div>
)}

Display Node Results

Show output values from each node:

{executionResult && executionResult.nodeResults.size > 0 && (
  <div className="node-results">
    <h4>Node Outputs</h4>
    {Array.from(executionResult.nodeResults.entries()).map(([nodeId, result]) => (
      <div key={nodeId} className="node-result">
        <strong>{nodeId}:</strong>
        <pre>{JSON.stringify(result.outputs, null, 2)}</pre>
      </div>
    ))}
  </div>
)}

What You’ve Built

✅ Complete visual workflow builder UI
✅ Drag-and-drop node palette
✅ Visual node connections
✅ Property editing panel
✅ Workflow execution with feedback
✅ Custom math and display nodes
✅ Error handling and status display

Next Steps

Creating Custom Nodes

Build more powerful custom nodes

Execution & Events

Master workflow execution

Serialization

Save/load workflows properly

Examples

See more complete examples

Troubleshooting

Nodes not showing in palette?

Make sure all node classes have the @defineNode decorator and are passed to the nodes prop.

Connections not working?

Verify port types match. An output of type 'number' can only connect to an input of type 'number' or 'any'.

Properties not editable?

Properties use @Property decorator, not @Input. Inputs are for connections, properties are for configuration.

Execution fails silently?

Check the browser console for errors. Add the onError callback to capture errors.

Getting Started

Core Concepts

Guides

Advanced

Your First Workflow Builder App

What We’ll Build

Prerequisites

Step 1: Create React Project

Step 2: Install CrystalFlow

Step 3: Configure TypeScript

Step 4: Create Custom Nodes

Number Input Node

Math Nodes

Display Node

Export All Nodes

Step 5: Create the Main App Component

Step 6: Add Styling

Step 7: Update Main Entry Point

Step 8: Run Your App

Using Your Workflow Builder

Adding Features

Save and Load Workflows

Add Progress Tracking

Display Node Results

What You’ve Built

Next Steps

Creating Custom Nodes

Execution & Events

Serialization

Examples

Troubleshooting

​What We’ll Build

​Prerequisites

​Step 1: Create React Project

​Step 2: Install CrystalFlow

​Step 3: Configure TypeScript

​Step 4: Create Custom Nodes

​Number Input Node

​Math Nodes

​Display Node

​Export All Nodes

​Step 5: Create the Main App Component

​Step 6: Add Styling

​Step 7: Update Main Entry Point

​Step 8: Run Your App

​Using Your Workflow Builder

​Adding Features

​Save and Load Workflows

​Add Progress Tracking

​Display Node Results

​What You’ve Built

​Next Steps

Creating Custom Nodes

Execution & Events

Serialization

Examples

​Troubleshooting

What We’ll Build

Prerequisites

Step 1: Create React Project

Step 2: Install CrystalFlow

Step 3: Configure TypeScript

Step 4: Create Custom Nodes

Number Input Node

Math Nodes

Display Node

Export All Nodes

Step 5: Create the Main App Component

Step 6: Add Styling

Step 7: Update Main Entry Point

Step 8: Run Your App

Using Your Workflow Builder

Adding Features

Save and Load Workflows

Add Progress Tracking

Display Node Results

What You’ve Built

Next Steps

Troubleshooting