title: react-redux: `state.get` is not a function
body: <p>I have reducers like below:</p>
  
  <pre><code>// SignIn.js
  const signIn = (state = {
    mobilePhone: {
      signInWay: 'email',
      countryCallingCode: '+65'
    }
  }, action) =&gt; {
    switch (action.type) {
      case 'SIGN_IN':
        return Object.assign({}, state, action.signInForm);
      default:
        return state;
    }
  };
  
  export default signIn;
  
  // UserInput.js
  const userInput = (state = {}, action) =&gt; {
    switch (action.type) {
      case 'USER_INPUT':
        return Object.assign({}, state, action.kv);
      default:
        return state;
    }
  };
  
  export default userInput;
  
  // Then index.js
  import { combineReducers } from 'redux';
  
  import userInput from './UserInput';
  import signIn from './SignIn';
  
  const gateApp = combineReducers({
    userInput,
    signInForm: signIn
  });
  
  export default gateApp;
  </code></pre>
  
  <p>Then in the <code>mapStateToProps</code>, when I tried to do</p>
  
  <pre><code>const mapStateToProps = (state) =&gt; {
    console.log(state)
    return {
      signInForm: state.get('signInForm')
    };
  };
  </code></pre>
  
  <p>I got error: <code>SignIn.js:9 Uncaught TypeError: state.get is not a function</code>, and I logged out the state object, it gave me something like this:</p>
  
  <p><a href="https://i.stack.imgur.com/h1Qgd.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/h1Qgd.jpg" alt="enter image description here"></a></p>
  
  <p>Where was going wrong?</p>