Tips for applying predicates to expanded entities in breeze

Question

Tips for applying predicates to expanded entities in breeze

Suppose I have an entity called Foo, which has a list of Bars. Each Bar also has a field named isDeleted to indicate whether it has been soft deleted. In my Javascript file using Breeze, I want to query for a specific Foo and filter out the soft deleted Bars. My attempt at achieving this was...

var query = breeze.EntityQuery.from('Foo')
        .where('Id', '==', id).and('Bars.IsDeleted', '==', false)
        .expand('Bars');

Unfortunately, this approach did not work. Can anyone guide me on how to accomplish this with Breeze? If the only solution is to create a method in the BreezeController and use standard LINQ syntax, I am willing to do that. However, I would like to explore if there is a way to make it work directly with Breeze first.

javascript c#linq breeze

Answer 1

Answer №1

At the moment, Breeze lacks the ability to filter 'expands', meaning that it cannot selectively return only the 'expanded' entities that meet specific criteria. This limitation is due to the fact that very few backend servers and persistence libraries offer support for such a functionality.

However, one potential workaround is to reverse the query to achieve the desired result. For example:

var query = breeze.EntityQuery.from('Bars').expand('Foo')
    .where(new breeze.Predicate('Foo.Id', 'eq', id)
                 .and('IsDeleted', 'eq', false));

This code assumes that each 'Bar' entity has a single 'Foo' property. By implementing this method, you can retrieve only the 'Bars' that meet the specified criteria along with their associated 'Foo' entity. This approach works by using nested scalar predicates like 'Foo.Id'.

Answer 2

At the moment, Breeze lacks the ability to filter 'expands', meaning that it cannot selectively return only the 'expanded' entities that meet specific criteria. This limitation is due to the fact that very few backend servers and persistence libraries offer support for such a functionality.

However, one potential workaround is to reverse the query to achieve the desired result. For example:

var query = breeze.EntityQuery.from('Bars').expand('Foo')
    .where(new breeze.Predicate('Foo.Id', 'eq', id)
                 .and('IsDeleted', 'eq', false));

This code assumes that each 'Bar' entity has a single 'Foo' property. By implementing this method, you can retrieve only the 'Bars' that meet the specified criteria along with their associated 'Foo' entity. This approach works by using nested scalar predicates like 'Foo.Id'.

Answer 3

Answer №2

When using multiple .where() chains on a query, they will automatically be combined with "AND". However, if you want to explicitly specify this logic, you can use the breeze.Predicate object as your where parameter like shown below:

var query = breeze.EntityQuery.from('Foo').expand('Bars')
    .where(new breeze.Predicate('Id', 'eq', id)
                     .and('Bars.IsDeleted', 'eq', false));

You also have the option to utilize other methods such as .or on the Predicate object, which chain together seamlessly.

Note: The following example demonstrates using multiple .where calls:

var query = breeze.EntityQuery.from('Foo').expand('Bars')
                .where('Id', 'eq', id)
                .where('Bars.IsDeleted', 'eq', false);

Answer 4

When using multiple .where() chains on a query, they will automatically be combined with "AND". However, if you want to explicitly specify this logic, you can use the breeze.Predicate object as your where parameter like shown below:

var query = breeze.EntityQuery.from('Foo').expand('Bars')
    .where(new breeze.Predicate('Id', 'eq', id)
                     .and('Bars.IsDeleted', 'eq', false));

You also have the option to utilize other methods such as .or on the Predicate object, which chain together seamlessly.

Note: The following example demonstrates using multiple .where calls:

var query = breeze.EntityQuery.from('Foo').expand('Bars')
                .where('Id', 'eq', id)
                .where('Bars.IsDeleted', 'eq', false);

Tips for applying predicates to expanded entities in breeze

Answer №1

Answer №2

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