score:1

Accepted answer

open will be in props not in state

change your render to this

<Dialog title="Welcome to the React App!" actions={actions} open={this.props.open} ></Dialog>

also in mapStateToProps function open value will be in state object so you don't need the second parameter in the function

function mapStateToProps(state) {
   return {
       open: state.checkPassword.open,
   };
}

score:1

When you are using redux and reading the value from store you need to use it from props in your component. In short you should not have a state that is directly derivable from props. Change your component to below and it should work

class StartDialog extends Component {

    render() {
       const actions = [ <FlatButton label="Submit" onClick={this.props.checkPassword} /> ];

       return (
          <Dialog title="Welcome to the React App!" actions={actions} open={this.props.open} ></Dialog>
       );
    }
}

Also in your mapStateToProps you need to access the state correctly, If you are using combineReducers, you need to access the open value from the corresponding reducer

So if you use combineReducer like

const reducers = combineReducer({
   checkPassword:checkpasswordReducer
})

you need to use your mapStateToProps function like

function mapStateToProps(state) {
   return {
       open: state.checkPassword.open,
   };
}

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