--- title: Methods description: The Flagship binding provides the following methods for evaluating feature flags. All methods are asynchronous and return a Promise. Evaluation methods never throw — they always return a value, falling back to the defaultValue you provide on errors. image: https://developers.cloudflare.com/dev-products-preview.png --- [Skip to content](#%5Ftop) Was this helpful? YesNo [ Edit page ](https://github.com/cloudflare/cloudflare-docs/edit/production/src/content/docs/flagship/binding/methods.mdx) [ Report issue ](https://github.com/cloudflare/cloudflare-docs/issues/new/choose) Copy page # Methods The Flagship binding provides the following methods for evaluating feature flags. All methods are asynchronous and return a `Promise`. Evaluation methods never throw — they always return a value, falling back to the `defaultValue` you provide on errors. Refer to the [types reference](https://developers.cloudflare.com/flagship/binding/types/) for the definitions of `FlagshipEvaluationContext` and `FlagshipEvaluationDetails`. ## `get()` Returns the raw flag value without type checking. Use this method when the flag type is not known at compile time. TypeScript ``` get(flagKey: string, defaultValue?: unknown, context?: FlagshipEvaluationContext): Promise ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | unknown | No | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const value = await env.FLAGS.get("checkout-flow", "v1", { userId: "user-42", }); ``` ## `getBooleanValue()` Returns the flag value as a `boolean`. TypeScript ``` getBooleanValue(flagKey: string, defaultValue: boolean, context?: FlagshipEvaluationContext): Promise ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | boolean | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const enabled = await env.FLAGS.getBooleanValue("dark-mode", false, { userId: "user-42", }); ``` ## `getStringValue()` Returns the flag value as a `string`. TypeScript ``` getStringValue(flagKey: string, defaultValue: string, context?: FlagshipEvaluationContext): Promise ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | string | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const variant = await env.FLAGS.getStringValue("checkout-flow", "v1", { userId: "user-42", country: "US", }); ``` ## `getNumberValue()` Returns the flag value as a `number`. TypeScript ``` getNumberValue(flagKey: string, defaultValue: number, context?: FlagshipEvaluationContext): Promise ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | number | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const maxRetries = await env.FLAGS.getNumberValue("max-retries", 3, { plan: "enterprise", }); ``` ## `getObjectValue()` Returns the flag value as a typed object. Use the generic parameter `T` to specify the expected shape. TypeScript ``` getObjectValue(flagKey: string, defaultValue: T, context?: FlagshipEvaluationContext): Promise ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | T | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` interface ThemeConfig { primaryColor: string; fontSize: number; } const theme = await env.FLAGS.getObjectValue( "theme-config", { primaryColor: "#000", fontSize: 14 }, { userId: "user-42" }, ); ``` Explain Code ## `getBooleanDetails()` Returns the flag value as a `boolean` with evaluation metadata. TypeScript ``` getBooleanDetails(flagKey: string, defaultValue: boolean, context?: FlagshipEvaluationContext): Promise> ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | boolean | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const details = await env.FLAGS.getBooleanDetails("dark-mode", false, { userId: "user-42", }); console.log(details.value); // true console.log(details.reason); // "TARGETING_MATCH" ``` ## `getStringDetails()` Returns the flag value as a `string` with evaluation metadata. TypeScript ``` getStringDetails(flagKey: string, defaultValue: string, context?: FlagshipEvaluationContext): Promise> ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | string | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const details = await env.FLAGS.getStringDetails("checkout-flow", "v1", { userId: "user-42", }); console.log(details.value); // "v2" console.log(details.variant); // "new" console.log(details.reason); // "TARGETING_MATCH" ``` ## `getNumberDetails()` Returns the flag value as a `number` with evaluation metadata. TypeScript ``` getNumberDetails(flagKey: string, defaultValue: number, context?: FlagshipEvaluationContext): Promise> ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | number | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` const details = await env.FLAGS.getNumberDetails("max-retries", 3, { plan: "enterprise", }); console.log(details.value); // 5 console.log(details.reason); // "TARGETING_MATCH" ``` ## `getObjectDetails()` Returns the flag value as a typed object with evaluation metadata. Use the generic parameter `T` to specify the expected shape. TypeScript ``` getObjectDetails(flagKey: string, defaultValue: T, context?: FlagshipEvaluationContext): Promise> ``` | Parameter | Type | Required | Description | | ------------ | ------------------------- | -------- | ------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | T | Yes | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules. | TypeScript ``` interface ThemeConfig { primaryColor: string; fontSize: number; } const details = await env.FLAGS.getObjectDetails( "theme-config", { primaryColor: "#000", fontSize: 14 }, { userId: "user-42" }, ); console.log(details.value); // { primaryColor: "#0051FF", fontSize: 16 } console.log(details.variant); // "brand-refresh" ``` Explain Code ## Error handling Evaluation methods never throw. They always return a value. When an error occurs, the method returns the `defaultValue` you provided. Use the `*Details` variants to inspect what went wrong. ### Type mismatch If you call a typed method on a flag with a different type (for example, `getBooleanValue` on a string flag), the method returns the default value. The `*Details` variants set `errorCode` to `"TYPE_MISMATCH"`. TypeScript ``` // Flag "checkout-flow" is a string flag, but you call getBooleanDetails. const details = await env.FLAGS.getBooleanDetails("checkout-flow", false); console.log(details.value); // false (the default value) console.log(details.errorCode); // "TYPE_MISMATCH" ``` ### Evaluation failure If evaluation fails for any other reason (for example, a network error or missing flag), the method returns the default value. The `*Details` variants set `errorCode` to `"GENERAL"`. TypeScript ``` const details = await env.FLAGS.getStringDetails( "nonexistent-flag", "fallback", ); console.log(details.value); // "fallback" console.log(details.errorCode); // "GENERAL" ``` ## Parameters reference The following table summarizes the parameters shared across all evaluation methods. | Parameter | Type | Required | Description | | ------------ | ------------------------- | ---------------- | --------------------------------------------------------------------------------------------- | | flagKey | string | Yes | The key of the flag to evaluate. | | defaultValue | varies | Yes (except get) | The fallback value returned if evaluation fails or the flag is not found. | | context | FlagshipEvaluationContext | No | Key-value attributes for targeting rules (for example, { userId: "user-42", country: "US" }). | ```json {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/flagship/","name":"Flagship"}},{"@type":"ListItem","position":3,"item":{"@id":"/flagship/binding/","name":"Binding API"}},{"@type":"ListItem","position":4,"item":{"@id":"/flagship/binding/methods/","name":"Methods"}}]} ```