CODEWITHSUNDEEP
node.jstypescriptsequelize.js
Andzej Maciusovic
Andzej Maciusovic

Reputation: 4476

Nodejs promises catch "hell" then using sequelize orm

Currently I developing web app for nodejs using popular sequelize orm and typesciprt. Here is a example from my code

this.createNewGame(player.idPlayer).then((game) => {

    this.getBestScore(player.idPlayer).then((bestScore) => {
         defer.resolve({
             idGame: game.idGame,
             bestScore: bestScore
         });
    }).catch((error) => { defer.reject(error); });

}).catch((error) => { defer.reject(error); });

Here is one of the method

private getBestScore(idPlayer: number): Q.Promise<number> {
    var defer = this.q.defer<number>();

    GameModel.max<number>('score', { where: { 'idPlayer': idPlayer } }).then((result) => {
        defer.resolve(result);
    }).catch((error) => { defer.reject(error); });

    return defer.promise;
}

I use catch in every method implementation and also in every call to method. I would like to have only one catch block in my expressjs router. I tried code like this and it works just fine, here is example:

//code in GameService class ...
getData(): Q.Promise<number> {
    var defer = this.q.defer<number>();

    this.method1().then((result) => {
        defer.resolve(result);
    });

    return defer.promise;
}

private method1(): Q.Promise<number> {
    var defer = this.q.defer<number>();

    throw 'some error occurs here';

    return defer.promise;
}

//router call GameService
router.get('/error-test', (req: express.Request, res: express.Response) => {

    gameService.getData().then((result) => {
        res.json(result);
    }).catch((error) => { res.send(error); });
    //works fine, here I get my thrown error

});

But in my previous example I need to use catch blocks everywhere otherwise If I get Unhandled rejection SequelizeDatabaseError or any other Unhandled rejection, nodejs stops working. Why I can't use only one catch block in my expressjs router when using calls to db with sequalize, like in my first example?

Upvotes: 0

Views: 480

Answers (1)

Jan Aagaard Meier
Jan Aagaard Meier

Reputation: 28798

Sequelize operations return promises, so there is no reason to put Q into the mix. This is equivalent

private getBestScore(idPlayer: number): Q.Promise<number> {
    return GameModel.max<number>('score', { where: { 'idPlayer': idPlayer } });
}

It doesn't return a Q.Promise (sequelize uses bluebird), but the implementations should be interoperable, since they are both 'thenables'.

Upvotes: 2

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