How to know if all the setState updates have been applied to the state in a React component?

I was reading the documentation about React setState, which says:

setState() does not immediately mutate this.state but creates a pending state transition. Accessing this.state after calling this method can potentially return the existing value.

Now I have a component like this:

class NoteScreenComponent extends React.Component {

    constructor() {
        super();
        this.state = { note: Note.newNote() }
    }

    componentWillMount() {
        this.setState({ note: this.props.note });
    }

    noteComponent_change = (propName, propValue) => {
        this.setState((prevState, props) => {
            let note = Object.assign({}, prevState.note);
            note[propName] = propValue;
            return { note: note }
        });
    }

    title_changeText = (text) => {
        this.noteComponent_change('title', text);
    }

    body_changeText = (text) => {
        this.noteComponent_change('body', text);
    }

    saveNoteButton_press = () => {
        // Save note to SQL database
        Note.save(this.state.note)
    }

    render() {
        return (
            <View>
                <TextInput value={this.state.note.title} onChangeText={this.title_changeText} />
                <TextInput value={this.state.note.body}  onChangeText={this.body_changeText} />
                <Button title="Save note" onPress={this.saveNoteButton_press} />
            </View>
        );
    }

}

What I'm wondering is, since setState does not update the state immediately, how can I know if the note I'm saving in saveNoteButton_press is the current version of the state? Is there some callback or something that I could poll to know if state has been fully updated?