Call a Function¶
Overview¶
You can call a function from a connected client application.
Usage¶
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 Client Application¶
To execute a function from the .NET Client SDK, use the user.Functions.CallAsync()
method, passing in the name of the function as the first parameter and the arguments
as the remaining parameters:
var bsonValue = await user.Functions.CallAsync("sum", 2, 40); // The result must now be cast to Int32: var sum = bsonValue.ToInt32(); // Or use the generic overloads to avoid casting the BsonValue: sum = await user.Functions.CallAsync<int>("sum", 2, 40);
The CallAsync() method returns a single BsonValue object, which you can
deserialize after calling the function or by using the the generic
overload. Both of these approaches to deserialization are shown in the
code above.
A BsonValue object can hold a single primitive value (as shown in the
example above), or hold a complete BSON document. If
you have a class that maps to the returned object, you can deserialize
to that class by using the generic overload. For example, the following code
calls a function that returns an object from a collection of "RealmTasks".
Since we know the shape of the returned object, we we can deserialize the
BsonValue to a class that we have created, and then we have
access to the properties and methods on that object:
var task = await user.Functions.CallAsync<MyClass> ("getTask", "5f7f7638024a99f41a3c8de4"); var name = task.Name;