@action-land/tarz 中文文档教程

Question

@action-land/tarz

提供更新功能的规范和基本类型类。 本质上有两种更新函数——

1. ReducerFunction: takes in action and state and returns a new state.
2. CommandFunction: takes in action and state and return a new action.

Index

• Types
• ReducerFunction
• CommandFunction
• Library Functions
• concatR
• concatC
• matchR
• matchC
• zeroR
• zeroC

Types

Reducer Function

1. Takes two arguments viz. Value and State.
2. Always return a State.
3. Does not mutate the original objects provided.

export type ReducerFunction<Value, State> = {
  (value: Value, state: State): State
}

Command Function

1. Takes two arguments only viz. Value and State.
2. Always returns an Action. It can consider returning Nil if no meaningful value is intended.
3. Does not mutate the original objects provided.

export type CommandFunction<Value, State, Output> = {
  (value: Value, state: State): Action<Output>
}

Library Functions

concatR

接受多个 ReducerFunction(s) 作为参数并返回一个新的 ReducerFunction 作为结果。

1. Consider the ReducerFunction(s) R0 R1 then two statements will be logically equivalent —
   1. concatR(R0, R1)(action, state)
   2. R1(action, R0(action, state))
2. Its associative — concatR(concatR(R0, R1), R2) === concatR(R0, concatR(R1, R2))
3. Its additive — concatR(R0, zeroR) === R0.

用法

import {concatR} from 'update-function-type'

const R0 = (a, b) => a + b
const R1 = (a, b) => a * b

concatR(R0, R1)(10, 20) // 10 * (10 + 20) === 300

concatC

接收多个 CommandFunction 作为参数并返回一个新的 CommandFunction 作为结果。

1. Consider the CommandFunction(s) C0 C1 then two statements will be logically equivalent —
   1. concatC(C0, C1)(action, state)
   2. List(C0(action, state), C1(action, state))
2. Its associative — concatC(concatC(C0, C1), C2) === concatC(C0, concatC(C1, C2))
3. Its additive — concatC(C0, zeroC) === C0

用法

import {concatC} from 'update-function-type'

const C0 = (a, b) => action('+', a + b)
const C1 = (a, b) => action('*', a * b)

concatC(C0, C1)(10, 500) // List(action('+', 510), action('B', 5000))

matchR

1. Takes in specification object with keys as action types and values as ReducerFunction(s) and returns another ReducerFunction.
2. The returned function when called with an Action and State internally calls the function matching the action's type.
3. The matching reducer function is called with value of the original action and the state is passed as is.
4. In case no action matches the given specification the original state is returned.

用法

import {matchR} from 'update-function-type'

const reducer = matchR({
  add: (a, b) => a + b,
  mul: (a, b) => a * b
})

reducer(action('add', 10), 1000) // returns 1010

matchC

1. Takes in specification object with keys as action types and values as CommandFunction(s) and returns another CommandFunction.
2. The returned function when called with an Action and State internally calls the function matching the action's type.
3. The matching reducer function is called with value of the original action and the state is passed as is.
4. In case no action matches the given specification Nil is returned.

用法

import {matchC} from 'update-function-type'

const reducer = matchC({
  add: (a, b) => action('added', a + b),
  mul: (a, b) => action('multiplied', a * b)
})

reducer(action('add', 10), 1000) // returns action('added', 1010)

zeroR

1. Is a ReducerFunction.
2. Takes in an action and a state and returns the same state.

zeroC

1. Is a CommandFunction.
2. Takes in an action and a state and returns the same action.