TakeLeading function

Fork TakeLeading(Function saga, { List? args, Map<Symbol, dynamic>? namedArgs, Function? Catch, Function? Finally, Channel? channel, dynamic pattern, bool detached = false, String? name, Result? result, })

Spawns a saga on each action dispatched to the Store or the channel provided that matches pattern. After spawning a task once, it blocks until spawned saga completes and then starts to listen for a pattern again.

In short, TakeLeading is listening for the actions when it doesn't run a saga.

• pattern is used to filter actions. Only matching actions will be processed. See docs for Take.

• saga is a Generator function.

• args and namedArgs are arguments to be passed to the started task. TakeEvery will add the incoming action to the argument list (i.e. the action will be a named {dynamic action} argument provided to saga)

• If a channel is provided then actions will be put from provided channel.

• Catch will be invoked for uncaught errors.

• Finally will be invoked in any case before task execution is end.

• If detached is false TakeLeading will return a forked task, otherwise it will return a spawned task. By default detached is false.

• name is an optional name for the task meta.

Example

In the following example, we create a basic task fetchUser. We use TakeLeading to start a new fetchUser task on each dispatched UserRequested action. Since TakeLeading ignores any new coming task after it's started, we ensure that if a user triggers multiple consecutive UserRequested actions rapidly, we'll only keep on running with the leading action

 import 'package:redux_saga/redux_saga.dart';
 import 'Api.dart';

 //...

 fetchUser({dynamic action}) sync* {
   // ...
 }

 watchLastFetchUser() sync* {
   yield TakeLeading(fetchUser, pattern: UserRequested);
 }

Notes

TakeLeading is a high-level API built using Take and Fork.

Implementation

Fork TakeLeading(Function saga,
    {List<dynamic>? args,
    Map<Symbol, dynamic>? namedArgs,
    Function? Catch,
    Function? Finally,
    Channel? channel,
    dynamic pattern,
    bool detached = false,
    String? name,
    Result? result}) {
  return Fork(_TakeLeading,
      args: <dynamic>[saga],
      namedArgs: <Symbol, dynamic>{
        #args: args,
        #namedArgs: namedArgs,
        #Catch: Catch,
        #Finally: Finally,
        #channel: channel,
        #pattern: pattern,
        #name: name
      },
      detached: detached,
      result: result);
}