Document query placeholder syntax

[alazier]

Would have helped with #500

[astigsen]

In general it seems like we could use a bit more detailed documentation about the query syntax. The cheatsheet at https://realm.io/news/nspredicate-cheatsheet/ is useful but contains lot of references to Cocoa that may be confusing for js users.

[appden]

Definitely agree with what @alazier said. We do have the query placeholder syntax documented in the filtered method documentation, but that's pretty much it.

[mehraj43]

can anyone please tell me what $0 means in this : this.state.subdivisions.filtered('subdivisionName CONTAINS[c] $0', this.state.nameFilter);

[mehraj43]

and what does [0] means is it for specifying array positions or something else and will be real help full if you could suggest me any tutorials or materials for Realm react native

[takameyer]

@mehraj43 The $n stands for the nth argument (0 based) after the given query string. For example:

"progressMinutes > $0 AND assignee == $1", 15, "Bart"

$0 is 15 $1 is "Bart"

I'll break down this specific example this.state.subdivisions.filtered('subdivisionName CONTAINS[c] $0', this.state.nameFilter);

This query is asking if the subdivisionName CONTAINS the value of this.state.nameFilter within itself (similar to the JavaScript string method includes). The [c] denotes that this check is case insensitive ("FooBar" CONTAINS[c] "oba" is true and "FooBar" CONTAINS "oba" is false)

There are many more examples of the Realm Query Language on this page: https://www.mongodb.com/docs/realm/realm-query-language/

RQL is based on a subset of NSPredicate. If the documentation is missing something, google searches for NSPredicate can also lead you in the right direction.

[mehraj43]

Thanks man for the help

[mehraj43]

const realm = new Realm({ path: 'UserDatabase.realm', schema: [ { name: 'user_details', properties: { user_id: {type: 'int', default: 0}, user_name: 'string', user_contact: 'string', user_address: 'string', }, }, ], });

can anyone explain me what does path mean in this and how to delete the schema if created

[mehraj43]

and does realm not generate object id like mongodb and how to create one if it cant generate and how to autoincrement it

[tomduncalf]

@mehraj43 Realm does not generate object IDs automatically, you don't necessarily need an id field on your Realm objects if you don't want, but to create one you can use the BSON module like so:

import { BSON } from "realm";

// ...

realm.create({
  id: new BSON.ObjectId()
  // ...
})

[tomduncalf]

@mehraj43

can anyone explain me what does path mean in this and how to delete the schema if created

The path indicates the name of the Realm file that will be created on disk (e.g. in the working directory on Node or in the app's documents folder on mobile) – this is where your data is actually stored. You can delete the Realm file by calling Realm.deleteFile(config), where config if the configuration you used to open the Realm (so in your example, you'd want to extract the config into a variable so you can reuse it). Of course you can also just delete the files manually.

Please could you open a new issue if you have problems that are not related to this (closed) issue?

[mehraj43]

i tried using realm in drawer navigation but my app keeps crashing so i installed realm@hermes through yarn now im getting this error Error: Exception in HostObject::get(propName:Realm): std::bad_alloc