React JS Warnings: Failed propType and uncontrolled input

Question

I'm struggling to fix some issues regarding React JS. Currently worked on a crash course, and I've been trying to improve the todoList. I'm very new and hopefully this might give me a new perspective after already 8 hours of troubleshooting.

My code - Input:

export class TodoItem extends Component {
getStyle = () => {
    return {
        background: '#233D4D',
        padding: '15px',
        borderBottom: '1px darkgray Ridge',
        textDecoration: this.props.todo.completed ? 'line-through' : 
 'none',
        color: this.props.todo.completed ? 'lightgreen' : 'white',
        fontWeight: this.props.todo.completed ? 'bold' : 'none',
    }
}

render() {
    const { title } = this.props.todo;
    return (
        <div style={this.getStyle()}>
            <p>
                <input type="checkbox" onChange= . 
    {this.props.markComplete.bind(this)} checked= . 
    {this.props.todo.completed} /> {'  '}
                {title}
                <button style={btnStyle} onClick= . 
    {this.props.delTodo.bind(this)}><FontAwesomeIcon size="2x" icon= . 
    {faTrash} /></button>
            </p>
        </div>
      )
     }
    }

   // PropTypes
   TodoItem.propTypes = {
   Todos: PropTypes.array.isRequired,
   markComplete: PropTypes.func.isRequired,
   delTodo: PropTypes.func.isRequired
   }

My code - Failed propType:

render() {
    const { title } = this.props.todo;
    return (
        <div style={this.getStyle()}>
            <p>
                <input type="checkbox" 
                onChange={this.props.markComplete.bind(this)} 
                checked={this.props.todo.completed} /> {'  '}
                {title}
                <button style={btnStyle} 
                onClick={this.props.delTodo.bind(this)}>
                <FontAwesomeIcon size="2x" icon={faTrash} />
                </button>
            </p>
        </div>
    )
}

// PropTypes
TodoItem.propTypes = {
    Todos: PropTypes.array.isRequired,
    markComplete: PropTypes.func.isRequired,
    delTodo: PropTypes.func.isRequired
}

Heres my issues:

#1 - Prop Types

index.js:1446 Warning: Failed prop type: The prop `Todos` is marked as required in `TodoItem`, but its value is `undefined`.
in TodoItem (at Todos.js:12)

#2 - Component changing an uncontrolled input

Warning: A component is changing an uncontrolled input of type text to 
be controlled. Input elements should not switch from uncontrolled to 
controlled (or vice versa). Decide between using a controlled or 
uncontrolled input element for the lifetime of the component.`

======== EDIT =========

Heres where the components called, properties passed and the manipulation:

render() {
    return (
      <Router>
        <div className="App">
          <div className="container">
            <Header />
            <Route exact path="/" render={props => (
              <React.Fragment>
                <AddTodo addTodo={this.addTodo} />
                <Todos todos={this.state.todo} markComplete= . 
                  {this.markComplete}
                  delTodo={this.delTodo} />
              </React.Fragment>
            )} />
            <Route path="/about" component={About} />
          </div>
        </div>
      </Router>
    );

class Todos extends Component {
  render() {
    // Mangler håndtering af ingen elementer
    let output = undefined;
    if(this.props.todos && this.props.todos.length > 0){
      // lav object
      let output = this.props.todos.map((todo) => (
        <TodoItem key={todo.id} todo={todo} markComplete= 
   {this.props.markComplete} delTodo={this.props.delTodo} />
      ))
      return output;
       }
       return (
        <div>
          {output}
        </div>
        /*this.props.todos.map((todo) => (
          <TodoItem key={todo.id} todo={todo} markComplete= 
  {this.props.markComplete} delTodo={this.props.delTodo} />
        ))*/
      );
    }
  }

Answer 1

I cleaned the mess in your code a bit and it is now working for me:

const TodoItem = ({title, completed, delTodo, markComplete}) => (
  <div>
    <p>
      <input type="checkbox" onChange={markComplete} checked={completed} />
      {title}
      <button onClick={delTodo}>Delete</button>
    </p>
  </div>
);

TodoItem.propTypes = {
  title: PropTypes.string.isRequired,
  completed: PropTypes.bool.isRequired,
  markComplete: PropTypes.func.isRequired,
  delTodo: PropTypes.func.isRequired
};

class Todos extends Component {
  constructor(props) {
    super(props);
    this.state = {
      todos: [
        {id: 1, title: "First", completed: false},
        {id: 2, title: "Second", completed: false},
        {id: 3, title: "Third", completed: true}
      ]
    };
  }

  markComplete = id => {
    const index = this.state.todos.findIndex(t => t.id === id);
    if (index > -1) {
      const modifiedTodos = JSON.parse(JSON.stringify(this.state.todos));
      modifiedTodos[index].completed = true;
      this.setState({todos: modifiedTodos});
    }
  };

  delTodo = id => {
    const index = this.state.todos.findIndex(t => t.id === id);
    if (index > -1) {
      const modifiedTodos = JSON.parse(JSON.stringify(this.state.todos));
      modifiedTodos.splice(index, 1);
      this.setState({todos: modifiedTodos});
    }
  };

  render() {
    return (
      <div>
        {this.state.todos
          ? this.state.todos.map(todo => (
              <TodoItem
                key={todo.id}
                title={todo.title}
                completed={todo.completed}
                markComplete={() => this.markComplete(todo.id)}
                delTodo={() => this.delTodo(todo.id)}
              />
            ))
          : null}
      </div>
    );
  }
}

Some comments about your code:

1. [FIRST ERROR]: Via propTypes you had Todos as property for TodoItem, but you didn't set that property when using TodoItem and because you set it as required with .isRequired, the first error had been thrown.
2. [SECOND ERROR]: As far as I can tell, changing from uncontrolled to controlled inputs happens, when the change handler changes from undefined to some function. You didn't paste your code with that function, so I can not tell, what was going wrong exactly, but I think the problem is the binding of the functions markComplete and delTodo you provided TodoItem via prop. Usually this binds the this object to the current execution context (class TodoItem in this case) and because TodoItem has no member functions markComplete and delTodo itself, the binding returns undefined for them.
3. Next time you post a question try to write a minimal working example (MWE). Your code is really bloated with irrelevant stuff. Remove that and the folks here at SO will have a much better time helping you.
4. In your classes Todos and TodoItem you don't have any state, so better use stateless function components (much more compact).
5. On some places you had white spaces and dots separating your property names and your property values.