Alias API in Mobile SDKs

Learn about the alias API call in Kotlin and Swift SDKs.

  •   3 minute read  

This guide explains how to use the alias API in Kotlin and Swift SDKs.

Overview

The RudderStack Kotlin and Swift SDKs provide an alias API that lets you merge different identities of a known user.

Note that:

  • You can use the alias event only for merging user identities. It does not update the user’s traits or other common properties.
  • RudderStack supports sending alias events only to certain downstream destinations. See the destination-specific documentation for more details.

Kotlin

The alias method definition in the Kotlin SDK is as follows:

analytics.alias(
    newId = "<newId>",
    previousId = "<previousId>",
    options = RudderOption()
)

The corresponding Java snippet is shown below:

analytics.alias("<newId>", "<previousId>", new RudderOption());

// Alias event with newId
analytics.alias(newId = "<newId>")

// Alias event with newId and previousId
analytics.alias(
    newId = "<newId>",
    previousId = "<previousId>"
)

// Alias event with newId and options
analytics.alias(
    newId = "<newId>",
    options = RudderOption(
        customContext = buildJsonObject {
            put("key", "value")
        },
        integrations = buildJsonObject {
            put("Amplitude", true)
            put("INTERCOM", buildJsonObject {
                put("lookup", "phone")
            })
        },
        externalIds = listOf(
            ExternalId(type = "<id_type>", id = "<value>")
        )
    )
)

Method signature

The below table describes the alias method signature in detail:

FieldData typeDescription
newIdStringNew user identifier (userId) associated with the user.
previousIdStringThe old user identifier.

Note: If not provided explicitly, the SDK automatically populates this field with the current userId or anonymousId.
optionsRudderOptionAdditional event options.

Example

A sample alias event sent from the Kotlin SDK is shown below:

analytics.alias(
    newId = "1hKOmRA4GRlm",
    previousId = "156K7m214GR2X",
    options = RudderOption()
)

analytics.alias("1hKOmRA4GRlm", "156K7m214GR2X", new RudderOption());

Swift

The alias method definition in the Swift SDK is as follows:

analytics.alias(
    newId: "<newId>",
    previousId: "<previousId>",
    options: RudderOption()
)
warning
Make sure to include the import RudderStackAnalytics statement before making the call.

The corresponding Objective-C snippet is shown below:

[analytics alias:@"<newId>" previousId:@"<previousId>" options:[[RSSOptionBuilder new] build]];
info
RSSOptionBuilder is an Objective-C–only helper class. It uses the builder pattern to create an RSSOption instance and lets you set custom context, configure integrations, and attach external IDs in a structured way.
// Alias event with newId
analytics.alias(newId: "Alias ID 1")

// Alias event with newId and previousId
analytics.alias(
    newId: "Alias ID 1",
    previousId: "Explicit Previous User ID 1"
)

// Alias event with newId and options
analytics.alias(
    newId: "Alias ID 1",
    options: RudderOption(
        integrations: [
            "Amplitude": true,
            "INTERCOM": [
                "lookup": "phone"
            ]
        ],
        customContext: [
            "key-1": "value-1"
        ],
        externalIds: [
            ExternalId(type: "brazeExternalId", id: "value1234")
        ]
    )
)

The corresponding Objective-C snippet is shown below:

// Alias event with newId
[analytics alias:@"Alias ID 1"];

// Alias event with newId and previousId
[analytics alias:@"Alias ID 1" previousId:@"Explicit Previous User ID 1"];

// Alias event with newId and options
RSSOptionBuilder *optionBuilder = [[RSSOptionBuilder alloc] init];

[optionBuilder setCustomContext:@{
    @"key-1": @"value-1"
}];

[optionBuilder setIntegrations:@{
    @"Amplitude": @YES,
    @"INTERCOM": @{
        @"lookup": @"phone"
    }
}];

[optionBuilder setExternalIds:@[
    [[RSSExternalId alloc] initWithType:@"brazeExternalId" id:@"value1234"]
]];

[analytics alias:@"Alias ID 1" options:[optionBuilder build]];

Method signature

The below table describes the alias method signature in detail:

FieldData typeDescription
newIdStringNew user identifier (userId) associated with the user.
previousIdStringThe old user identifier.

Note: If not provided explicitly, the SDK automatically populates this field with the current userId or anonymousId.
optionsRudderOptionAdditional event options.

Example

A sample alias event sent from the Swift SDK is shown below:

analytics.alias(
    newId: "Alias ID 1",
    previousId: "Explicit Previous User ID 1",
    options: RudderOption(
        integrations: [
            "Amplitude": true,
            "INTERCOM": [
                "lookup": "phone"
            ]
        ],
        customContext: [
            "key-1": "value-1"
        ],
        externalIds: [
            ExternalId(type: "brazeExternalId", id: "value1234")
        ]
    )
)

RSSOptionBuilder *optionBuilder = [[RSSOptionBuilder alloc] init];

[optionBuilder setCustomContext:@{
    @"key-1": @"value-1"
}];

[optionBuilder setIntegrations:@{
    @"Amplitude": @YES,
    @"INTERCOM": @{
        @"lookup": @"phone"
    }
}];

[optionBuilder setExternalIds:@[
    [[RSSExternalId alloc] initWithType:@"brazeExternalId" id:@"value1234"]
]];

[analytics alias:@"Alias ID 1"
         previousId:@"Explicit Previous User ID 1"
            options:[optionBuilder build]];

Questions? Contact us by email or on Slack