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72 lines
5.0 KiB
Markdown
72 lines
5.0 KiB
Markdown
---
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id: custom_activation_strategy
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title: Custom Activation Strategies
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---
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:::tip
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This document is a reference for custom activation strategies. If you're looking for a guide on how to use them, see the [_how to use custom strategies_ guide](../how-to/how-to-use-custom-strategies.md).
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:::
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**Custom activation strategies** let you define your own activation strategies to use with Unleash. When the [built-in activation strategies](../user_guide/activation-strategies.md) aren't enough, custom activation strategies are there to provide you with the flexibility you need.
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Custom activation strategies work exactly like the built-in activation strategies when working in the admin UI.
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## Definition
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You define custom activation strategies on your Unleash instance, either via the admin UI or via the API. A strategy contains:
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- A strategy **name**: You'll use this to refer to the strategy in the UI and in code.
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- An optional **description**: Use this to describe what the strategy should do.
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- An optional list of **parameters**: Use this to provide the strategy with arguments it should use in its evaluation.
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The strategy **name** is the only required parameter, but adding a good **description** will make it easier to remember what a strategy should do. The list of **parameters** lets you pass data from the Unleash instance to the strategy implementation.
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### Parameters
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Parameters let you provide arguments to your strategy that it can access for evaluation. When creating a strategy, each parameter can be either required or optional. This marking is to help the user understand what they need to fill out; they can still save the strategy without filling out a required field.
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Each parameter consists of three parts:
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- a **name**: must be unique among the strategy's parameters.
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- an optional **description**: describe the purpose or format of the parameter.
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- a parameter **type**: dictates the kind of input field the user will see in the admin UI and the type of the value in the implementation code.
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#### Parameter types
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Each parameter has one of five different parameter types. A parameter's type impacts the kind of controls shown in the admin UI and how it's represented in code.
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Here's an overview over how the types are represented in the JSON payload returned from the Unleash server. The exact types will vary based on your programming language's type system.
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:::note Unset values
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Values of *all types* have an empty string (`""`) as the default value. As such, if you don't interact with a control or otherwise set a value, the value will be an empty string, regardless of the value's type.
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:::
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| type name | code representation | example value | UI control |
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|------------|----------------------------------------|---------------|--------------------------|
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| string | `string` | `"a string"` | A standard input field |
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| percentage | an `int` between 0 and 100 (inclusive) | `99` | A value slider |
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| list | `string` (values are comma-separated) | `"one,two"` | A multi-input text field |
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| number | `string` | `"123"` | A numeric text field |
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| boolean | `"true"` or `"false"` | `"true"` | An on/off toggle |
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## Implementation
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:::note
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If you have not implemented the strategy in your client SDK, the check will always return `false` because the client doesn't recognize the strategy.
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:::
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While custom strategies are _defined_ on the Unleash server, they must be _implemented_ on the client. All official Unleash client SDKs provide a way for you to implement custom strategies. You should refer to the individual SDK's documentation for specifics, but for an example, you can have a look at the [_Node.js client implementation_ section in the _how to use custom strategies_ guide](../how-to/how-to-use-custom-strategies.md#step-3-a).
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The exact method for implementing custom strategies will vary between SDKs, but the server SDKs follow the same patterns. For front-end client SDKs ([Android](../sdks/android-proxy.md), [JavaScript](../sdks/proxy-javascript.md), [React](../sdks/proxy-react.md), [iOS](../sdks/proxy-ios.md)), the custom activation strategy must be implemented in the [Unleash Proxy](../sdks/unleash-proxy.md).
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When implementing a strategy in your client, you will get access to the strategy's parameters and the Unleash Context. Again, refer to your specific SDK's documentation for more details.
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