Breeze Predicate in sub query

I have two entities, let's call them Alpha and Beta.

There is a one to many relationship between them, such that Beta has a foreign key to Alpha, MyAlphaId, and thus a reference property MyAlpha.

I have a predicate being built for Alphas.

e.g.

var predicateAlpha = new Predicate('name', 'contains', 'somevalue'); 

I want to then "transpose" this onto a query for Beta's where its myAlpha property matches that predicate.

e.g.

var predicateBeta = new Predicate('myAlpha', 'in', predicateAlpha); 

I am aware of the ability for me to construct the predicate in the following manner:

var predicateBeta = new Predicate('myAlpha.name', 'contains', 'somevalue'); 

My issue is that I don't know what that predicate may be. I can't just pre-pend 'myAlpha.' as it may include an OData function such as 'concat('somefield', 'someotherfield')'.

Any other thoughts or suggestions on how I can achieve this?

For me, it would make sense for IN to accept a predicate that allows this to happen... I can't see the source code accepting a predicate so I can't think how else to make this happen...

1 Answer

Assuming that Alpha has a property betas, you could query for Alphas using the predicate, and expand the Betas so that they are brought in too. Then collect the Betas if you need them in a single list:

var query = em.createQuery(predicateAlpha).expand('betas'); var betas = []; em.executeQuery(query).then(queryResult => { queryResult.results.forEach(alpha => { betas = betas.concat(alpha.betas); }); });