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ngrx-query

ngrx-query is a library for querying and managing network state in Angular (2+) applications that use ngrx. It is a port of the redux-query library - many thanks to redux-query for coming up with a very useful library. For an in-depth explanation of what problems redux-query (and, by extension, ngrx-query) solve, read Introducing redux-query.

Check out the demo to see the final outcome, but the real power of this library is the reduction of boilerplate code.

With ngrx-query you can:

  • Declare your network dependencies right next to your Angular components. Data is requested automatically when components mount. When components update and unmount, in-flight requests are automatically cancelled the subscription is automatically unsubscribed. TODO: check if in-flight requests really are cancelled.
  • Trigger server-side changes (mutations) by dispatching regular Redux actions.
  • Have a consistent, minimal-boilerplate interface for all network-related state.
  • Transform and normalize data to avoid duplicate state.
  • Perform optimistic updates.
  • Use with other ngrx libraries like @ngrx/effects.
  • Debug network state and actions with Redux dev tools like ngrx-store-logger or the Redux Devtools browser extension.

Getting Started

Install ngrx-query via npm:

$ npm install --save ngrx-query

Add the entitiesReducer and queriesReducer to your combined reducer.

Import the NgrxQueryModule.forRoot() in your root AppModule.

For example:

@NgModule({
  // ...
  imports: [
    // ...
    StoreModule.forRoot({
      entities: entitiesReducer,
      queries: queriesReducer,
    }),
    NgrxQueryModule.forRoot(),
  ],
})
export class AppModule {}

Dependencies

All dependencies are listed in package.json. @angular/core, @angular/http, @ngrx/store (^4.0.2) and @ngrx/effects (^4.0.2) are peer dependencies. HTTP requests are made using @angular/http's Http service.

Global config

NgrxQueryModule.forRoot() optionally accepts an NgrxQueryConfig object.

// functions must be exported and named in order build with AoT
export function queriesSelector(state) {
  return state.my.path.to.queries;
}
export function entitiesSelector(state) {
  return state.my.path.to.entities;
}

@NgModule({
  // ...
  imports: [
    // ...
    NgrxQueryModule.forRoot({
      // Determines where to locate the queries in the store
      // Must match the location of the queriesReducer
      // default: (state) => state.queries
      queriesSelector: queriesSelector,

      // Determines where to locate the entities in the store
      // Must match the location of the entitiesReducer
      // default: (state) => state.entities
      entitiesSelector: entitiesSelector,

      // Determines how much to delay between retry attempts
      // default: { maxAttemps: 5, maxDuration: 5000, minDuration: 300 }
      backoff: {
        maxAttempts: 3, // number of attempts
        maxDuration: 1000, // ms
        minDuration: 300, // ms
      },

      // Determines which status codes on a GET response will trigger a retry
      // default: [
      //   UNKNOWN = 0, // normally means a failed connection
      //   REQUEST_TIMEOUT = 408, // client took too long
      //   TOO_MANY_REQUESTS = 429, // hopefully backoff stops this getting worse
      //   SERVICE_UNAVAILABLE = 503,
      //   GATEWAY_TIMEOUT = 504,
      // ]
      retryableStatusCodes: [ 408 ],
    }),
  ],
})
export class AppModule {}

Usage and API

Requests and mutations

There are two types of queries with ngrx-query: "requests" and "mutations". Requests are for reading values from HTTP endpoints. Mutations are for HTTP endpoints that change network state – the "C", "U", and "D" in "CRUD".

Requests can be triggered from the nqConnect attribute directive, the ConnectService or a requestAsync action. Mutations are triggered by the ConnectService or by dispatching a mutateAsync action.

By default, requests are GETs and mutations are POSTS.

Query configs

Query configs are objects used to describe how ngrx-query should handle the request or mutation. Query config options differ slightly between requests and mutations

Request query config options

Name Type Required? Description
url string yes The URL for the HTTP request.
transform function Function that transforms the response data to an entities object where keys are entity IDs and values are entity data. Can be used to normalize data.
update object yes Object where keys are entity IDs and values are update functions.
body object The request body.
force boolean Perform the request even if we've already successfully requested it.
queryKey string The identifier used to identify the query metadata in the queries reducer. If unprovided, the url and body fields are serialized to generate the query key.
meta object Various metadata for the query. Can be used to update other reducers when queries succeed or fail.
options object Options for the request. Set options.method to change the HTTP method, options.headers to set any headers and options.credentials = 'include' for CORS.

Mutation query config options

Name Type Required? Description
url string yes The URL for the HTTP request.
transform function Function that transforms the response data to an entities object where keys are entity IDs and values are entity data. Can be used to normalize data.
update object yes Object where keys are entity IDs and values are update functions.
optimisticUpdate object Object where keys are entity IDs and values are functions that provide the current entity value. The return values are used to update the entities store until the mutation finishes.
body object The HTTP request body.
queryKey string The identifier used to identify the query metadata in the queries reducer. If unprovided, the url and body fields are serialized to generate the query key.
options object Options for the request. Set options.method to change the HTTP method, options.headers to set any headers and options.credentials = 'include' for CORS.

transform functions

transform functions let you process and normalize response data before it is passed to the update step. They have the following signature:

(responseJson: ?Object, responseText: string) => { [key: string]: any }

If your data is normalized on the server, you may not need to use this function.

update functions

update functions are responsible for reconciling response data with the existing entities reducer data for the given entity ID. They have the following signature:

(prevValue: any, transformedValue: any) => any

The prevValue is whatever value is selected from the entities reducer for the respective entity ID. The returned value from this function will become the new value for the entity ID in the entities reducer.

optimisticUpdate functions

optimisticUpdate functions are just like update functions except they only pass the prevValue:

(prevValue: any) => any

ngConnect

Use the nqConnect attribute directive to declare network dependencies for an Angular component. nqConnect takes a request query config object. Example usage:

// TODO

connectRequest passes an extra prop to the child component: forceRequest. Calling this function will cause the request(s) to be made again. This may be useful for polling or creating an interface to trigger refreshes.

mutateAsync

Dispatch mutateAsync Redux actions to trigger mutations. mutateAsync takes a mutation query config as its only argument. Example usage with an Angular component:

// TODO

requestAsync

Similarly to how mutations are triggered by dispatching mutateAsync actions, you can trigger requests by dispatching requestAsync actions with a request query config.

Example

A simple example is included. To run it, simply:

$ npm install
$ npm run start