# Variation Distribution

When running an A/B Test, you need to distribute users across Variations and implement the logic for each Variation. You can perform this user distribution through the Hackle SDK.

## Variation

{% hint style="warning" %}
Server SDKs do not support cohort targeting. If targeting includes a cohort, run the test using a Client SDK.
{% endhint %}

By passing an **Experiment Key** and **user** to the `Variation()` method, you can distribute the user and receive the result. Then implement logic for each Variation.

In the example code below, Experiment Key 42 is passed, the User Identifier is "ae2182e0", and two Variations, A and B, exist.

```go
import "github.com/hackle-io/hackle-go-sdk/hackle"

// 실험 키가 42인 A/B 테스트에서
// "ae2182e0"라는 식별자를 가진 사용자에게 노출할 테스트 그룹을 결정합니다.
// 결정하지 못하는 상황인 경우 테스트 그룹 A를 반환합니다.
user := hackle.NewUserBuilder().ID("ae2182e0").Build()
variation := hackleClient.Variation(42, user)

// 할당받은 그룹에 대한 로직
if variation == "A" {
  // 그룹 A 로직
} else {
  // 그룹 B 로직
}
```

## VariationDetail

The `VariationDetail()` method works the same as the `Variation()` method and additionally provides the reason for assignment to a specific Variation. This method is useful for checking whether distribution is working correctly.\
You must pass the Experiment Key as a parameter. In the example code below, Experiment Key 42 is passed.

```go
import "github.com/hackle-io/hackle-go-sdk/hackle"

// 분배 결정 상세
decision := hackleClient.VariationDetail(42, user)

// 분배 그룹
variation = decision.Variation()

// 분배 결정 사유
reason := decision.Reason()
```

The distribution decision reason is returned in the form of **`SDK_NOT_READY`**. Refer to 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>

## Parameter Settings

* You can also receive the parameter values of the distributed Variation through the `VariationDetail()` method.
* Since parameter values configured on the Hackle A/B Test screen exist as key-value pairs, you can use the methods below according to the configured parameter type to receive and use the configured parameter value.

### GetString

* Returns parameter values configured as STRING or JSON type.
* Returns the value configured for the distributed Variation.

```go
import "github.com/hackle-io/hackle-go-sdk/hackle"

decision := hackleClient.VariationDetail(42, user)

stringValue := decision.GetString("string_key", "default_value")
jsonValue := decision.GetString("json_key", "{}")
```

### GetNumber

* Returns the parameter value configured as Number type as a float64 type.
* Returns the value configured for the distributed Variation.

```go
import "github.com/hackle-io/hackle-go-sdk/hackle"

decision := hackleClient.VariationDetail(42, user)

number := decision.GetNumber("number_key", 42.0)
```

### GetBool

* Returns parameter values configured as bool type.
* Returns the value configured for the distributed Variation.

```go
import "github.com/hackle-io/hackle-go-sdk/hackle"

decision := hackleClient.VariationDetail(42, user)

boolValue := decision.GetBool("bool_key", false)
```


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