React native - local-mongoDb - Cannot Read property undefined - mongodb

Question

I don't know why this get an error.
I should take from local-mongodb library a new _id of my future new postIt and run new page but in "this.props.onInsertNewPost(idPost);" it get an error (Cannot Read property idPost undefined).
onInsertNewPost call a redux function that set "id" in the initialState.
I tried using binding (this.idPost=this.idPost.bind(this)) anche call idPost() function in componentWillMout, but it get the same problem
componentWillMount(){
return new Promise((resolve,reject)=>{
setTimeout(()=>{
db.loadDatabase(err=>{
var obj={
year : this.state.year,
month : this.state.month,
day : this.state.day,
houre : this.state.houre,
minute : this.state.minute,
text : '',
isSelected : false,
imagesStored : []
};
db.insert(obj,function(err,doc){
let docDoc=JSON.stringify(doc);
let parseDoc=JSON.parse(docDoc);
console.log(parseDoc._id);
idPost=parseDoc._id;
this.props.onInsertNewPost(idPost);
console.log('create nuovo post');
resolve('componentDidMoutnewPostit');
});
});
},100);
});
};

Answer 1

I think this problem occured because idPost is global.
if you pass parseDoc._id directly into your onInsertNewPost function it should work.
componentWillMount(){
return new Promise((resolve,reject)=>{
setTimeout(()=>{
db.loadDatabase(err=>{
var obj={
year : this.state.year,
month : this.state.month,
day : this.state.day,
houre : this.state.houre,
minute : this.state.minute,
text : '',
isSelected : false,
imagesStored : []
};
db.insert(obj,function(err,doc){
let docDoc=JSON.stringify(doc);
let parseDoc=JSON.parse(docDoc);
console.log(parseDoc._id);
this.props.onInsertNewPost(parseDoc._id);
console.log('create nuovo post');
resolve('componentDidMoutnewPostit');
});
});
},100);
});
};