redux在react中的使用方法（入門級）

在控制台中列印redux

const redux =

require
('redux'
)console.
log(redux.
createstore((
)=>))
// 至少傳入乙個函式 -- reducer --- 純函式
// dispatch:  觸發修改狀態的方式
// subscribe: 訂閱 -- 資料改變，要以何種方式 更新檢視
// getstate: 獲取狀態

import

from
'redux'
/** * 如果需要獲取狀態  store.getstate()
* 如果需要訂閱 更新檢視  store.subscribe(fn)  fn是關鍵 （狀態/屬性的改變會引起檢視的二次渲染 ---  入口檔案）
* 如果需要觸發更改狀體啊  store.dispatch()
*/

const defaultstate =

const
reducer
=(state = defaultstate, action)
=>
case
'decrement'
:return object.
assign
(, state,
)default
:return state
}}export
default reducer

import

from
'redux'
import reducer from
'./reducer'
const store =
createstore
(reducer)
export
default store

import react from

'react'
import reactdom from
'react-dom'
import store from
'./redux/store'
function
render()
render()
// 如果狀態一旦發生改變，就重新執行 render 函式（自定義函式）
store.
subscribe
(render)

import react,

from
'react'
import store from
'./store'
export
default
class
extends
component)}
}>
-<
/button>
}>
+<
/button>
<
/div>)}
}

以todolist為例

1.入口檔案

import react from

'react'
import reactdom from
'react-dom'
'./todolist/todolist'
import
from
'react-redux'
// 頂級元件中使用
import store from
'./todolist/store' 
reactdom.
render
(>
>
<
/provider>
,  document.
getelementbyid
('root'
))

const defaultstate =

const
reducer
=(state = defaultstate, action)
=>
case
'remove_item'
:const arr = state.list.
filter
((item, index)
=>
)return
default
:return state
}}export
default reducer

import

from
'redux'
import reducer from
'./reducer'
export
default
createstore
(reducer)

import react,

from
'react'
import
from
'react-redux'
class
form
extends
component
handlerchange
=(e)
=>)}
handlerkeyup
=(e)
=>
}render()
onchange =
onkeyup =
/>)}
}const
mapdispatchtoprops
= dispatch =>)}
}}// 如果不需要獲取狀態，第乙個引數寫為null
export
default
connect
(null
, mapdispatchtoprops)
(form)

import react,

from
'react'
import
from
'react-redux'
class
list
extends
component
}// removedata = () => 
render()
>
>刪除<
/button>
}>刪除 */
}<
/li>))
}<
/ul>)}
}const
mapstatetoprops
= state =>
}const
mapdispatchtoprops
= dispatch =>)}
}}export
default
connect
(mapstatetoprops, mapdispatchtoprops)
(list)

觀測 redux 原始碼，得知，自動呼叫一次dispatch

// when a store is created, an "init" action is dispatched so that every

// reducer returns their initial state. this effectively populates
// the initial state tree.
dispatch
()

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