> For the complete documentation index, see [llms.txt](https://docs.hackle.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hackle.io/en/development-guide/ios/ios-variation.md).

# Variation Distribution

When running an A/B Test, you need to distribute users across variations and write logic for each variation. You can use the Hackle SDK to handle this distribution.

## variation

Pass the **Experiment Key** to the `variation()` method to distribute the user and receive the result.

<table><thead><tr><th width="150">Parameter</th><th width="120">Type</th><th width="110">Required</th><th>Constraints</th></tr></thead><tbody><tr><td>Experiment Key (key)</td><td><code>int</code></td><td>Required</td><td>-</td></tr></tbody></table>

#### Example

The example code below passes Experiment Key 42, where there are two variations: A and B.

{% tabs %}
{% tab title="Swift" %}

```swift
// Decides the variation to expose to the user in the A/B Test with Experiment Key 42.
// Returns variation A if the variation cannot be decided.
let variation = hackleApp.variation(experimentKey: 42)

// Logic for the assigned variation
if variation == "A" {
  // Logic for variation A
} else if variation == "B" {
  // Logic for variation B
}
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
// Decides the variation to expose to the user in the A/B Test with Experiment Key 42.
// Returns variation A if the variation cannot be decided.
NSString *variation = [app variationWithExperimentKey:42];

// Logic for the assigned variation
if([variation isEqual:@"A"]) {
    // Logic for variation A
} else if ([variation isEqual:@"B"]) {
    // Logic for variation B
}
```

{% endtab %}
{% endtabs %}

## variationDetail

The `variationDetail()` method works the same as `variation()` but also provides the reason for the distribution decision. This method is useful for verifying that distribution is working correctly.

<table><thead><tr><th width="150">Parameter</th><th width="120">Type</th><th width="110">Required</th><th>Constraints</th></tr></thead><tbody><tr><td>Experiment Key (key)</td><td><code>int</code></td><td>Required</td><td>-</td></tr></tbody></table>

#### Example

You must pass the Experiment Key as a parameter. The example code below passes Experiment Key 42.

{% tabs %}
{% tab title="Swift" %}

```swift
// Distribution decision detail
let decision: Decision = hackleApp.variationDetail(experimentKey: 42)

// Assigned variation
let variation: String = decision.variation

// Reason for the distribution decision
let reason: String = decision.reason
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
// Distribution decision detail
HackleDecision *decision = [hackleApp variationDetailWithExperimentKey:42];

// Assigned variation
NSString *variation = [decision variation];

// Reason for the distribution decision
NSString *reason = [decision reason];
```

{% endtab %}
{% endtabs %}

### Distribution Reason

The distribution reason is returned in the format **`SDK_NOT_READY`**. See the table below for details.

<table><thead><tr><th width="319.12109375">Distribution Reason</th><th width="305.35546875">Description</th><th>Distribution Result</th></tr></thead><tbody><tr><td><code>SDK_NOT_READY</code></td><td><p>The SDK is not ready to use.</p><p>(e.g., initialization attempted with an invalid SDK Key)</p></td><td>A (Control Group)</td></tr><tr><td><code>EXPERIMENT_NOT_FOUND</code></td><td>No A/B Test was found for the provided Experiment Key. The Experiment Key may be incorrect, or the experiment may be archived.</td><td>A (Control Group)</td></tr><tr><td><code>NOT_IN_MUTUAL_EXCLUSION_EXPERIMENT</code></td><td>The experiment is included in Mutually Exclusive Settings, but<br>the user was not assigned to that Mutually Exclusive Group.</td><td>A (Control Group)</td></tr><tr><td><code>EXPERIMENT_DRAFT</code></td><td>The A/B Test is in draft state.</td><td>A (Control Group)</td></tr><tr><td><code>EXPERIMENT_PAUSED</code></td><td>The A/B Test is paused.</td><td>A (Control Group)</td></tr><tr><td><code>EXPERIMENT_COMPLETED</code></td><td>The A/B Test has ended.</td><td>Winning Variation selected at completion</td></tr><tr><td><code>OVERRIDDEN</code></td><td>The user was assigned to a specific group<br>by Override.</td><td>Override-assigned<br>group</td></tr><tr><td><code>NOT_IN_EXPERIMENT_TARGET</code></td><td>The user is not an A/B Test target.</td><td>A (Control Group)</td></tr><tr><td><code>TRAFFIC_NOT_ALLOCATED</code></td><td>The A/B Test is running, but<br>the user was not allocated to the test.</td><td>A (Control Group)</td></tr><tr><td><code>TRAFFIC_ALLOCATED</code></td><td>The user has been allocated to the A/B Test.</td><td>Allocated group</td></tr><tr><td><code>VARIATION_DROPPED</code></td><td>The originally allocated group has been removed from the test.</td><td>A (Control Group)</td></tr><tr><td><code>INVALID_INPUT</code></td><td>The input value is invalid.</td><td>A (Control Group)</td></tr><tr><td><code>EXCEPTION</code></td><td>An unknown error occurred.</td><td>A (Control Group)</td></tr></tbody></table>

### Parameters

{% hint style="info" %}
This feature is supported in iOS SDK 2.9.0 and above.
{% endhint %}

* The `variationDetail()` method also returns the parameter values for the assigned variation.
* The `Decision` instance returned by `variationDetail()` contains a `ParameterConfig` object with all parameter configuration.
* Since parameters set on the Hackle A/B Test screen exist as key-value pairs, you can use the methods below to retrieve parameter values according to the configured parameter type.
* You can query the configured values for the assigned variation using the functions below.

<table data-header-hidden><thead><tr><th width="136.12109375">Type</th><th>Description</th></tr></thead><tbody><tr><td><code>getString</code></td><td>Returns a parameter value configured as STRING or JSON type.</td></tr><tr><td><code>getInt</code></td><td>Returns a parameter value configured as NUMBER type as an Int.</td></tr><tr><td><code>getDouble</code></td><td>Returns a parameter value configured as NUMBER type as a Double.</td></tr><tr><td><code>getBool</code></td><td>Returns a parameter value configured as Bool type.</td></tr></tbody></table>

#### Example

{% tabs %}
{% tab title="Swift" %}

```swift
let decision: Decision = hackleApp.variationDetail(experimentKey: 42)
let config: ParameterConfig = decision.config

let strValue: String = decision.getString(forKey: "parameter_key_string_type", defaultValue: "defaultValue")
let strValueInConfig: String = config.getString(forKey: "parameter_key_string_type", defaultValue: "defaultValue")

let jsonValue: String = decision.getString(forKey: "parameter_key_json_type", defaultValue: "defaultValue")
let jsonValueInConfig: String = config.getString(forKey: "parameter_key_json_type", defaultValue: "defaultValue")

let intValue: Int = decision.getInt(forKey: "parameter_key_number_type", defaultValue: 0)
let intValueInConfig: Int = config.getInt(forKey: "parameter_key_number_type", defaultValue: 0)

let doubleValue: Double = decision.getDouble(forKey: "parameter_key_number_type", defaultValue: 0.0)
let doubleValueInConfig: Double = config.getDouble(forKey: "parameter_key_number_type", defaultValue: 0.0)

let boolValue: Bool = decision.getBool(forKey: "parameter_key_boolean_type", defaultValue: false)
let boolValueInConfig: Bool = config.getBool(forKey: "parameter_key_boolean_type", defaultValue: false)
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
HackleDecision *decision = [hackleApp variationDetailWithExperimentKey:42];

NSString *stringValue = [decision getStringForKey:@"parameter_key_string_type" defaultValue:@"defaultValue"];

NSString *jsonValue = [decision getStringForKey:@"parameter_key_json_type" defaultValue:@"defaultValue"];
```

{% endtab %}
{% endtabs %}


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