如何重构瀑布.then()

Question

这里的代码使用动作加载数据,并且会是系列的,但是编辑这段代码很难添加另一个API加载,语法也不清楚.

this.props.loadNutMatrixes({perPage:'all'}).then(()=>{
      this.props.loadIngredients().then(()=>{
        this.props.getBadge().then(()=>{
          this.props.loadNutInfoItems({perPage:'all'}).then(()=>{
            this.props.getItemSize().then(()=>{
              this.props.getSingleMenuCategory(this.props.category_uid).then(()=>{
                this.props.loadAllStores(({per_page:'all'})).then(()=>{
                  if (this.props.selectedMenuItem ){
                    initialize("addNewMenuItem", {
                      ...this.props.selectedMenuItem
                    })
                  }
                })
              })
            })
          })
        })
      })
    })

Answer 1

您可以通过链接promises而不是嵌套将其转换为垂直结构:

this.props.loadNutMatrixes({perPage:'all'})
  .then(() => this.props.loadIngredients())
  .then(() => this.props.getBadge())
  .then(() => this.props.loadNutInfoItems({perPage:'all'}))
  .then(() => this.props.getItemSize())
  .then(() => this.props.getSingleMenuCategory(this.props.category_uid))
  .then(() => this.props.loadAllStores(({per_page:'all'})))
  .then(() => {
    if (this.props.selectedMenuItem) {
      initialize("addNewMenuItem", {
        ...this.props.selectedMenuItem
      })
    }
  });

可能的改进可能是将所有接受参数的promise创建函数包装到没有参数的函数中,并将其作为props相反的方式传递:

loadAllNutMatrixes() {
  return this.loadNutMatrixes({ perPage: 'all' });
}

loadAllNutInfoItems() {
  return this.loadNutInfoItems({ perPage: 'all' });
}

getSingleMenuCategoryFromId() {
  return this.getSingleMenuCategory(this.category_uid);
}

loadEveryStory() {
  return this.loadAllStores({ perPage: 'all' });
}

然后你可以将最后一步重构为它自己的方法:

onChainFinished() {
  if (this.props.selectedMenuItem) {
    initialize("addNewMenuItem", {
      ...this.props.selectedMenuItem
    })
  }
}

并将两者结合起来进行一些解构,以实现更清洁的链条:

const { props } = this;
props.loadAllNutMatrixes()
  .then(props.loadIngredients)
  .then(props.getBadge)
  .then(props.loadAllNutInfoItems)
  .then(props.getItemSize)
  .then(props.getSingleMenuCategoryFromId)
  .then(props.loadEveryStore)
  .then(this.onChainFinished);

根据您的评论编辑

使用promise.all之类的东西,但是以串联的方式!

链接Promises没有本机方法,但您可以构建适合您的用例的帮助方法来执行此操作.这是一个一般的例子:

// `cp` is a function that creates a promise and 
// `args` is an array of arguments to pass into `cp`
chainPromises([
  { cp: this.props.loadNutMatrixes, args: [{perPage:'all'}] },
  { cp: this.props.loadIngredients },
  { cp: this.props.getBadge },
  { cp: this.props.loadNutInfoItems, args: [{perPage:'all'}] },
  { cp: this.props.getItemSize },
  { cp: this.props.getSingleMenuCategory, args: [this.props.category_uid] },
  { cp: this.props.loadAllStores, args: [{per_page:'all'}] }
]).then(() => {
  if (this.props.selectedMenuItem) {
    initialize("addNewMenuItem", {
      ...this.props.selectedMenuItem
    })
  }
});

function chainPromises(promises) {
  return promises.reduce(
    (chain, { cp, args = [] }) => {
      // append the promise creating function to the chain
      return chain.then(() => cp(...args));
    }, Promise.resolve() // start the promise chain from a resolved promise
  );
}

如果您使用与上面相同的方法来重构带有参数的方法,它也会清除此代码:

const { props } = this;
chainPropsPromises([
  props.loadAllNutMatrixes,
  props.loadIngredients,
  props.getBadge,
  props.loadAllNutInfoItems,
  props.getItemSize,
  props.getSingleMenuCategoryFromId,
  props.loadEveryStory
])
.then(this.onChainFinished);

function chainPropsPromises(promises) {
  return promises.reduce(
    (chain, propsFunc) => (
      chain.then(() => propsFunc());
    ), Promise.resolve()
  );
}