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I'm working on a project using Google firebase firestore. I wanna implement a filter on my search for users. Imagine the search for only active users with a checkbox which users can select.

let db = Firestore.firestore()
let reference = db.collection("users").limit(to: 20)
//FILTER
if showOnlyActiveUsersBtn.isSelected {
    reference.whereField("active", isEqualTo: true)
}
reference.getDocuments(completion: {(querySnapshot, error) in
    .....
})

I expected this would return the result with only users who have the field "active: true", however, it returned the same list as the query without the filter... if I write like:

let db = Firestore.firestore()
let reference = db.collection("users").limit(to: 20).whereField("active", isEqualTo: true)
reference.getDocuments(completion: {(querySnapshot, error) in
    .....
})

It returns the result I expected first. I don't have any idea why my filter doesn't work. How can I add logical "AND" condition with user-friendly way?

YMO
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1 Answers1

12

Firestore Query objects are immutable, meaning that they can never be modified after they are created. In your code, you aren't remembering the new query you built with whereField. Instead, you need to build a new Query object on top of an existing query, and remember the new one:

let db = Firestore.firestore()
var reference = db.collection("users").limit(to: 20)
if showOnlyActiveUsersBtn.isSelected {
    // build a new query using the old query, reassign to reference
    reference = reference.whereField("active", isEqualTo: true)
}
reference.getDocuments(completion: {(querySnapshot, error) in
    .....
})

If you don't like using var instead of let, I'm sure you can find a way to rework this sample. In any event, you will need to remember the new query returned by whereField, and use that to call getDocuments.

Doug Stevenson
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  • Doug Thanks! I didn't know Firestore Query objects are immutable. Your answer will help not only me but also others who don't know that :) Thank you! – YMO Sep 02 '18 at 05:42