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Pinia ​

流程图 ​

https://cdn.jsdelivr.net/gh/yxw007/BlogPicBed@master//img/20220414113917.jpg 地址：https://drive.google.com/file/d/1ELfAkS9kyDyGLA9U5lbooVqEwne2xK8G/view?usp=sharing

工作流程 ​

  1. 第一阶段：注册 + 初始化pina和plugin
  2. 第二阶段：预设store配置，返回useStore函数
  3. 第三阶段：使用store，驱动store的初始化流程
    1. 创建Store：使用reactive({}) 创建一个响应式对象
    2. 执行setup：
      1. state：全部转为Ref，让计算属性跟踪state中值的变化
      2. 合并state、actions 至store中
      3. 遍历getters，将其用computed包裹一层，调用并返回
      4. 合并getters 至store中
    3. 合并公共接口($patch$state$reset$subscribe$onAction$dispose)至store中
    4. 返回store，并将其store缓存至存储所有storepinia._s() 中

功能剖析 ​

1. $dispose：其实就是调用store的scopeEffect.stop 停止所有关联的effect 属性(getters) ​

jsx
//1. 使用
store.$dispose();

//2. 实现逻辑
$dispose: () => {
			scope.stop();
			actionSubscribes = [];
			pinia._s.delete(id); // 删除store, 数据变化了不会在更新视图
}

2. $onAction：捕获所有的action操作（典型的发布订阅模式） ​

  • 使用

    jsx
    const { increment } = store;

const handleClick = () => {
  //1.触发action
	increment();
};

//2. 订阅回调
store.$onAction(({ after, onError, name }) => {
	console.log("action执行了", name);

	after((result) => {
		console.log("状态已经更新完毕了", result);
	});

	onError(() => {
		console.log("出错");
	});
});
    jsx
    <button @click="handleClick">点击增加</button>

  • 实现原理

    1. 收集订阅

      jsx
      let actionSubscribes = []
const store = {
	  ...
    //1. 收集订阅
		$onAction: addSubscription.bind(null, actionSubscribes),
}
      jsx
      //订阅
export function addSubscription(subscriptions, cb) {
	subscriptions.push(cb);
	return function reomveSubscription() {
		const idx = subscriptions.indexOf(cb);
		if (idx > -1) {
			subscriptions.splice(idx, 1);
		}
	}
}

//发布
export function triggerSubscription(subscriptions, ...args) {
	subscriptions.forEach(cb => cb(...args));
}

    2. 包裹action一层，让action调用时触发发布动作

      jsx
      ...
for (let key in store) {
		const prop = store[key]; 
		if (typeof prop === 'function') {// 对action可以进行扩展 aop思想
			store[key] = wrapAction(key, prop);
		}
}

function wrapAction(name, action) {
		return function () {
			const afterCallbackList = [];
			const onErrorCallbackList = [];

			function after(callback) {
				afterCallbackList.push(callback)
			}

			function onError(callback) {
				onErrorCallbackList.push(callback)
			}
			
		  //发布
			triggerSubscription(actionSubscribes, { after, onError, store, name }); 

			let ret
			try {
				ret = action.apply(store, arguments); 
			} catch (error) {
				triggerSubscription(onErrorCallbackList, error)
			}

			if (ret instanceof Promise) {
				return ret.then((value) => {
					triggerSubscription(afterCallbackList, value)
				}).catch(error => {
					triggerSubscription(onErrorCallbackList, error);
					return Promise.reject(error)
				})
			} else {
				triggerSubscription(afterCallbackList, ret)
			}

			return ret;
		}
	}

3. $subscribe：利用watch包裹store.state 一层，做到监控所有的state变化，然后发布即可 ​

  • 使用

    jsx
    const store = useCounterStore();
store.$subscribe((dispatchInfo, state) => {
	console.log("数据变化 dispatchInfo:", dispatchInfo);
	console.log("数据变化 state:", state);
});

const { increment } = store;
const handleClick = () => {
	increment();
};
    jsx
    <button @click="handleClick">点击增加</button>

  • 触发效果

    "img"

  • 实现原理

    jsx
    const store = {
	  ...
		$subscribe(callback, options) {  
			scope.run(() => watch(pinia.state.value[id], state => { // 监控状态变化
				callback({ type: 'dirct' }, state);
			}, options))
		}
}

4. $patch：批量更新，避免性能消耗 ​

  • 使用

    jsx
    const store = useCounterStore();

function patchUpdate(){
	//方式一：传方法
   store.$patch(() => {
		store.count++;
		store.fruits.push("橘子");
	});
	
	//方式二：传属性
	/* let fruits = [...store.fruits, "橘子"];
		store.$patch({
			count: ++store.count,
			fruits,
		}); */
}
    jsx
    <button @click="patchUpdate">批量更新</button>

  • 实现原理

    jsx
    const Store = {
  ...
  $patch
}

function $patch(partialStateOrMutation) {
		if (typeof partialStateOrMutation === 'function') { // 这个方法一般用的比较少
			partialStateOrMutation(store);
		} else {
			//递归深度合并对象
			mergeReactiveObject(store, partialStateOrMutation);
		}
}

function mergeReactiveObject(target, partialState) { // 递归
	for (let key in partialState) {
		if (!partialState.hasOwnProperty(key)) continue; // 如果是原型上的不考虑
		const oldValue = target[key];
		const newValue = partialState[key];
		
		if (isObject(oldValue) && isObject(newValue) && !isRef(newValue) && !isReactive(newValue)) {
			target[key] = mergeReactiveObject(oldValue, newValue)
		} else {
			target[key] = newValue;
		}
	}
	return target
}

5. $reset：重置state ​

  • 使用

    jsx
    store.$reset();

  • 实现原理

    jsx
    let { state, getters, actions } = options;
// 注意： reset 不能在setupStore 方式创建的store中使用 原因：无法获取到初始状态
store.$reset = function () { 
		const newState = state ? state() : {};
		store.$patch((oldState) => {
			Object.assign(oldState, newState);
		})
}

6. $state: 重新赋值state ​

注意：原来的state还会遗漏在state中，因为底层采用Object.assign合并的

  • 使用

    jsx
    store.$state = { count: 100, fruits: [] };

  • 实现原理：将新状态state合并至老store中

    jsx
    Object.defineProperty(store, '$state', {
		get: () => {
			// 只要状态
			return pinia.state.value[id];
		}, 
		set: (state) => {
			return $patch(oldStore => Object.assign(oldStore, state));
		},
})

function $patch(partialStateOrMutation) {
		if (typeof partialStateOrMutation === 'function') { // 这个方法一般用的比较少
			partialStateOrMutation(store);
		} 
    ...
}

7. mapActions：映射store中的方法 ​

  • 使用

    jsx
    import { useCounterStore } from "../stores/counter";
import { mapActions, mapState } from "@/pinia";
export default {
	methods: {
		...mapActions(useCounterStore, ["increment"]),
	},
};

  • 实现原理：利用function将action将store中的方法包裹一层

    jsx
    export function mapActions(useStore, keysOrMapper) {
	return Array.isArray(keysOrMapper) ? keysOrMapper.reduce((reduced, key) => {
		//说明：利用function包裹一层
		reduced[key] = function (...args) {
			return useStore()[key](...args);
		}
		return reduced
		// {count:function(){ useStore()['count']}}
	}, {}) : Object.keys(keysOrMapper).reduce((reduced, key) => {
		reduced[key] = function (...args) {
			const store = useStore();
			const storeKey = keysOrMapper[key];
			return store[storeKey](...args)
		}
		return reduced
	}, {})
}

8. mapState：映射store中的state的方法 ​

  • 使用

    jsx
    import { useCounterStore } from "../stores/counter";
import { mapActions, mapState } from "@/pinia";
export default {
	computed: {
		...mapState(useCounterStore, ["count"]), 
	}
};

  • 实现原理： 利用function包裹一层，然后映射到store属性上

    jsx
    export function mapState(useStore, keysOrMapper) {
	const store = useStore();
	return Array.isArray(keysOrMapper) ? keysOrMapper.reduce((reduced, key) => {
    //说明：利用function包裹一层，然后映射到store属性上
		reduced[key] = function () {
			return store[key];
		}
		return reduced
	}, {}) : Object.keys(keysOrMapper).reduce((reduced, key) => {
		reduced[key] = function () {
			const storeKey = keysOrMapper[key];
			return store[storeKey]
		}
		return reduced
	}, {})
}

9. mapWritableState：映射store中state 可读可写的方法 ​

  • 使用

    jsx
    import { useCounterStore } from "@/stores/counter";
import { mapActions, mapState, mapWritableState } from "@/pinia";
export default {
	computed: {
		...mapWritableState(useCounterStore, ["count"]), 
	}
};

<button @click="count++">点击</button>

  • 实现原理：映射成对象，然后利用get set 进行读写

    jsx
    export function mapWritableState(useStore, keysOrMapper) {
	const store = useStore();
	return Array.isArray(keysOrMapper) ? keysOrMapper.reduce((reduced, key) => {
		reduced[key] = {
			get() {
				return store[key];
			},
			set(value) {
				store[key] = value
			}
		}
		return reduced
	}, {}) : Object.keys(keysOrMapper).reduce((reduced, key) => {
		reduced[key] = {
			get() {
				const storeKey = keysOrMapper[key];
				return store[storeKey]
			},
			set(value) {
				const storeKey = keysOrMapper[key];
				store[storeKey] = value
			}
		}
		return reduced
	}, {})
}

Released under the MIT License.

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