用 axios 搜索：新字符时取消之前的请求

Question

我有一个搜索栏，每个字母都会更新结果，但是当用户快速输入 3 个字母时，之前的请求不会被取消，所以在他得到结果之前会有一个难看的延迟。

我已阅读此https://github.com/axios/axios#cancellation，也许我有点累，但我很难将它添加到我的项目中。它几乎起到了相反的效果，现在它需要永远。 您有什么建议或者您推荐一个好的教程以便我理解这一点吗？

<input v-model="query" type="text" class="form-control" placeholder="Runner name or description"
                   aria-label="Runner name or description"
                   aria-describedby="basic-addon2">


watch: {
            query: {
                handler: _.debounce(function () {
                    this.newSearch()
                }, 100)
            }
        },
methods: {
            searchItems() {
                let filters = {
                    q: this.query
                };

                const CancelToken = axios.CancelToken;
                const source = CancelToken.source();

                axios.post('/Items/find', filters, {
                    cancelToken: source.token
                })
                .catch(function(thrown) {
                    if (axios.isCancel(thrown)) {
                        console.log('Request canceled', thrown.message);
                    }
                })
                .then(
                    response => {
                        if(this.Items!=null){
                            response.data.forEach(element => {
                                this.Items.push(element);
                            });
                        }
                        else
                            this.Items=response.data;
                    }
                );
            },
            newSearch(){
                const CancelToken = axios.CancelToken;
                const source = CancelToken.source();
                source.cancel('Cancel previous request');

                this.countItems();
                this.searchItems();
            },
            showMore(){
                this.startindex = this.startindex+this.nbrows;
                this.searchItems();
            },
            countItems(){
                this.countItems=10;
                let filters = {
                    q: this.query
                };
                axios.post('/Items/count', filters).then(
                    response => {
                        this.countItems=response.data;
                    }
                );
            }
        }

Answer 1

问题是您在 newSearch 中创建了一个新的 canceltoken 并取消了它而不是原来的那个。 如果您将源代码保存在 Vue 组件上，您可以检查 newSearch（如果存在），然后再取消。 发布 Promise 完成后，您将再次删除源，以便在不需要（或可能）时无法取消。

{
  searchItems() {
      let filters = {
          q: this.query
      };

      const CancelToken = axios.CancelToken;
      this.searchItemsSource = CancelToken.source();

      axios.post('/Items/find', filters, {
          cancelToken: this.searchItemsSource.token
      })
      .catch(function(thrown) {
          if (axios.isCancel(thrown)) {
              console.log('Request canceled', thrown.message);
          }
      })
      .then(
          response => {
              this.searchItemsSource = undefined;
              if(this.Items!=null){
                  response.data.forEach(element => {
                      this.Items.push(element);
                  });
              }
              else
                  this.Items=response.data;
          }
      );
  },
  newSearch(){
      if (this.searchItemsSource) {
          this.searchItemsSource.cancel('Cancel previous request');
      }
      this.countItems();
      this.searchItems();
  },
}

关于此代码的附注；我实际上会将取消上一个请求移到 searchItems 方法中，因为同时有两个正在运行的调用是没有意义的。它看起来更像这样：

{
  searchItems() {
      let filters = {
          q: this.query
      };

      if (this.searchItemsSource) {
          this.searchItemsSource.cancel('Cancel previous request');
      }
      const CancelToken = axios.CancelToken;
      this.searchItemsSource = CancelToken.source();

      axios.post('/Items/find', filters, {
          cancelToken: this.searchItemsSource.token
      })
      .catch(function(thrown) {
          if (axios.isCancel(thrown)) {
              console.log('Request canceled', thrown.message);
          }
      })
      .then(
          response => {
              this.searchItemsSource = undefined;
              if(this.Items!=null){
                  response.data.forEach(element => {
                      this.Items.push(element);
                  });
              }
              else
                  this.Items=response.data;
          }
      );
  },
  newSearch(){
      this.countItems();
      this.searchItems();
  },
}

此时您可以问问自己是否需要 newSearch 方法，您可以删除它并将 countItems 调用也移到 searchItems 中。不过，这一切都取决于您的其余代码和功能。

Answer 2

我能够让它工作。诀窍是在启动 API 调用之前检查取消令牌是否存在。我不得不将 CancelToken 和 cancel 变量移到外面Vue 对象/组件..

---

此示例在 GitHub 上搜索存储库...

var cancel;
var CancelToken = axios.CancelToken;

new Vue({
  el: "#app",
  data: {
    query: "",
    results: "",
    isLoading: false
  },
  methods: {
    clear() {
      this.isLoading = false;
      this.results = "";
      this.query = "";
    },

    handleSearch: _.debounce(function() {
      this.preApiCall();
    }, 300),

    preApiCall() {
      if (cancel != undefined) {
        cancel();
        console.log("cancelled");
      }
      this.apiCall(this.query);
    },

    apiCall(query) {
      if (query !== "") {
        this.isLoading = true;
        axios({
          method: "get",
          url: "https://api.github.com/search/repositories",
          cancelToken: new CancelToken(function executor(c) {
            cancel = c;
          }),
          params: {
            q: query
          }
        }).then(res => {
          this.results = JSON.parse(JSON.stringify(res.data.items));
          this.isLoading = false;
        }).catch(err => {
          this.results = err.message;
          throw Error(err.message);
          this.isLoading = false;
        });
      } else {
        this.clear();
      }
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.6.10/vue.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.18.0/axios.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

<div id="app">
  <input v-model="query" @keyup.stop="handleSearch" type="text" class="form-control" placeholder="Search">
  <button @click.stop="clear">Clear</button>
  <div v-if="isLoading">Loading...</div>
  <ul v-if="results !== ''">
    <li v-for="(r, index) in results" :key="index">
      {{ r.name }}
    </li>
  </ul>
</div>

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[CodePen mirror]

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已取消的请求：