Call a Function

Overview

You can call a function from other parts of your Realm app, from a connected client application, or with Realm CLI.

The examples in this section demonstrate calling a simple function named sum that takes two arguments, adds them, and returns the result:

// sum: adds two numbers
exports = function(a, b) {
  return a + b;
};

Call from A Function, Trigger, or HTTP Endpoint

You can call a function from another function, including HTTPS endpoints and triggers, by accessing function context with the context.functions interface:

// difference: subtracts b from a using the sum function
exports = function(a, b) {
    return context.functions.execute("sum", a, -1 * b);
};

Call from a JSON Expression

You can call a function from a rule expression, including service rules, by using the %function operator:

{
  "numGamesPlayed": {
    "%function": {
      "name": "sum",
      "arguments": [
        "%%root.numWins",
        "%%root.numLosses"
      ]
    }
  }
}

Call from Realm CLI

To call a function with Realm CLI, run realm-cli function run and specify the function name and any arguments. The command returns the function result as EJSON as well as any log or error messages.

realm-cli function run \
 --function=sum \
 --user=61a50d82532cbd0de95c7c89 \
 --args=1 --args=2

realm-cli function run \
 --function=sum \
 --args=1 --args=2

Call from a Client Application

You can call a function from client applications that are connected with a Client SDK or over the wire protocol.