Query Scopes

Definition

Query scopes are a way to encapsulate query constraints in your entities while giving them readable names .

A Practical Example

For instance, let's say that you need to write a report for subscribers to your site. Maybe you track subscribers in a users table with a boolean flag in a subscribed column. Additionally, you want to see the oldest subscribers first. You keep track of when a user subscribed in a subscribedDate column. Your query might look as follows:

var subscribedUsers = getInstance( "User" )
    .where( "subscribed", true )
    .orderBy( "subscribedDate" )
    .get();

Now nothing is wrong with this query. It retrieves the data correctly and you continue on with your day.

Later, you need to retrieve a list of subscribed users for a different part of the site. So, you write a query like this:

var subscribedUsers = getInstance( "User" )
    .where( "subscribed", true )
    .get();

We've duplicated the logic for how to retrieve active users now. If the database representation changed, we'd have to change it in multiple places. For instance, what if instead of keeping track of a boolean flag in the database, we just checked that the subscribedDate column wasn't null?

var subscribedUsers = getInstance( "User" )
    .whereNotNull( "subscribedDate" )
    .get();

Now we see the problem. Let's look at the solution.

The key here is that we are trying to retrieve subscribed users. Let's add a scope to our User entity for subscribed:

component extends="quick.models.BaseEntity" {

    function scopeSubscribed( query ) {
        return query.where( "subscribed", true );
    }

}

Now, we can use this scope in our query:

var subscribedUsers = getInstance( "User" )
    .subscribed()
    .get();

We can use this on our first example as well, for our report.

var subscribedUsers = getInstance( "User" )
    .subscribed()
    .orderBy( "subscribedDate" )
    .get();

We've successfully encapsulated our concept of a subscribed user!

We can add as many scopes as we'd like. Let's add one for longestSubscribers.

component extends="quick.models.BaseEntity" {

    function scopeLongestSubscribers( query ) {
        return query.orderBy( "subscribedDate" );
    }

    function scopeSubscribed( query ) {
        return query.where( "subscribed", true );
    }

}

Now our query is as follows:

var subscribedUsers = getInstance( "User" )
    .subscribed()
    .longestSubscribers()
    .get();

Best of all, we can reuse those scopes anywhere we see fit without duplicating logic.

Usage

All query scopes are methods on an entity that begin with the scope keyword. You call these functions without the scope keyword (as shown above).

Each scope is passed the query, a reference to the current QueryBuilder instance, as the first argument. Any other arguments passed to the scope will be passed in order after that.

component extends="quick.models.BaseEntity" {

    function scopeOfType( query, type ) {
        return query.where( "type", type );
    }

}

var subscribedUsers = getInstance( "User" )
    .ofType( "admin" )
    .get();