Accessing array property in "named query" in hyperledger-composer - hyperledger-composer

Question

In my hyperledger composer app I want to write a named query that returns all persons with a certain hobby.
The model for "Person" is the following:
participant Person identified by id {
o String id
o String firstName
o String lastName
o String email
--> Hobby[] hobbies optional
}
The model for "Hobby" is the following:
asset Hobby identified by name {
o String name
}
The named query has the following structure:
query selectPersonsByHobby {
description: "Select all persons with a certain hobby."
statement:
SELECT org.comp.myapp.Person
WHERE //don't know what to put here//
}
I don't know what to put after the "WHERE" operator in order to achieve what I want.
I want something like the following:
query selectPersonsByHobby {
description: "Select all persons with a certain hobby."
statement:
SELECT org.comp.myapp.Person
WHERE (hobbies.contains(_$hobby))
}
Is this even possible ?

Answer 1

The short answer is that this query should work:
query selectConsultantsBySkill {
description: "Select all persons with a certain hobby."
statement:
SELECT org.comp.myapp.Person
WHERE (hobbies CONTAINS _$targetHobby)
}
But note that because your hobbies is an array of Relationships the targetHobby parameter will have to be something like resource:org.acme.Hobby#cycling . In a production scenario you would be 'calling' the query from a UI program so you could pre-pend the relationship syntax.
I guess this is just a test example, but I wonder if Hobby needs to be a relationship? It would be easier if not.
You could alternatively use a concept (and even an enumerated type within the concept!). Here is an example of a modified model and query with a concept:
participant Person identified by id {
o String id
o String firstName
o String lastName
o String email
o Interest[] passTime
}
concept Interest {
o String name
o String description
}
query selectConsultantsBySkill {
description: "Select all persons with a certain hobby."
statement:
SELECT org.comp.myapp.Person
WHERE (passTime CONTAINS (name == _$targetHobby ))
}