Vue.js 和 D3.js - 力模拟

Question

我目前正在尝试使用 Restful-Api 调用并使用信息来进行 d3.js 强制模拟。问题是，如果我使用来自 API 的数据，如果什么都没有，调用模拟处理它。如果我等待下一个滴答声this.$nextTick(simu)，所有位置最终都会变成NaN。这种行为有原因吗？

const URL = 'https://jsonplaceholder.typicode.com/posts';

new Vue({
  el: '#app',
  data() {
    return {
      webGraph: {
        nodes: [],
        edges: []
      },
      graph1: {
        nodes:[
          {url:2},
          {url:3},
        ],
        edges:[
          {source:2, target:3},
        ]
      }
    }
  },
  created() {
    axios.get(URL).then((response) => {
      let node1 = {
        url: response.data[1].id
      }
      let node2 = {
        url: response.data[2].id
      }
      let edge = {
        source: {url:response.data[1].id},
        target: {url:response.data[2].id}
      }
      this.webGraph.nodes.push(node1)
      this.webGraph.nodes.push(node2)
      this.webGraph.edges.push(edge)
    })
    
  d3.forceSimulation(this.webGraph.nodes)
      .force("charge", d3.forceManyBody().strength(-25))
      .force("link", d3.forceLink().id(d => d.url).links(this.webGraph.edges))
      .on('end', function() {
        console.log("done")
      });
  d3.forceSimulation(this.graph1.nodes)
      .force("charge", d3.forceManyBody().strength(-25))
      .force("link", d3.forceLink().id(d => d.url).links(this.graph1.edges))
      .on('end', function() {
        console.log("done")
      });
  

  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/6.2.0/d3.min.js"></script>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>

<div id="app">
  <h6>{{webGraph}}</h6>
  <br> 
  <h6>{{graph1}}</h6>
</div>

Answer 1

webGraph和graphData1产生不同结果的原因是webGraph的模拟在它有数据之前就开始了。如果您将simulation 代码移到axios.get().then 内，那么您会看到它按预期工作。

const URL = 'https://jsonplaceholder.typicode.com/posts';

new Vue({
  el: '#app',
  data() {
    return {
      webGraph: {
        nodes: [],
        edges: []
      },
      graph1: {
        nodes:[
          {url:2},
          {url:3},
        ],
        edges:[
          {source:2, target:3},
        ]
      }
    }
  },
  created() {
    axios.get(URL).then((response) => {
      let node1 = {
        url: response.data[1].id
      }
      let node2 = {
        url: response.data[2].id
      }
      let edge = {
        source: node1,
        target: node2
      }
      
      this.webGraph = {
        nodes: [node1, node2],
        edges: [edge]
      };
      
      d3.forceSimulation(this.webGraph.nodes)
        .force("charge", d3.forceManyBody().strength(-25))
        .force("link", d3.forceLink().id(d => d.url).links(this.webGraph.edges))
        .on('end', function() {
          console.log("done")
        });
    })

  d3.forceSimulation(this.graph1.nodes)
      .force("charge", d3.forceManyBody().strength(-25))
      .force("link", d3.forceLink().id(d => d.url).links(this.graph1.edges))
      .on('end', function() {
        console.log("done")
      });
  

  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/6.2.0/d3.min.js"></script>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>

<div id="app">
  <h6>{{webGraph}}</h6>
  <br> 
  <h6>{{graph1}}</h6>
</div>

在您的代码中，我还更改了edge 的初始化。它表明您需要查看 variables 和 references 之间的区别。

使用let edge = { source: {url:response.data[1].id}, target: {url:response.data[2].id} }，如果node1 更改，edge.source 不会。所以edge.source 不知道指向哪里。使用let edge = { source: node1, target: node2 }，代码不仅更短，而且如果node1 更改，edge.source 始终是最新的。