javascript - 在 d3 中链接转换的正确方法是什么？

Question

受此启发 other question ，我创建了一个动画 ( jsfiddle ) 来绘制一个圆，然后是一条将它连接到另一个圆的线。我读到 D3 v3 不需要监听 end 事件以进行链式转换。

下面的代码可以工作，但我应该如何重构它才能使其不使用 end 事件？

var margin = {top: 40, bottom: 40, left: 40, right: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.bottom - margin.top;

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var t0 = svg.append("circle")
    .attr("r", 0)
    .attr("cx", 40)
    .attr("cy", 40)
    .attr("class", "point")
  .transition()
    .duration(500)
    .attr("r", 4);

var t1 = t0.each("end", function(){ 
    var t2 = svg.append("path")
        .style("stroke", "#000")
        .style("stroke-width", 2)
        .style("fill", "none")
        .attr("d", "M40,40L40,40")
      .transition()
        .ease("linear")
        .duration(500)
        .attr("d", "M40,40L80,80");

    t2.each("end", function(){ 
        svg.append("circle")
            .attr("r", 1)
            .attr("cx", 80)
            .attr("cy", 80)
            .attr("class", "point")
          .transition()
            .duration(500)
            .attr("r", 4);
    });
});

Answer 1

好的，感谢评论，我意识到我可以做到这一点:

• 附加第一项并使用 t0 = svg.transition() 创建第一个转换，
• 附加第二个项目并创建第二个转换(将在 t0 结束后触发)t1 = t0.transition()
• 对第三项重复 t2 = t1.transition()

请注意，如果要更改每个过渡的持续时间，必须在定义时完成。这是错误的:

var t1 = t0.transition()
    .ease("linear");
t1.select("path.line")
    .duration(500)
    .attr("d", "M40,40L80,80");

应该是:

var t1 = t0.transition()
    .ease("linear");
    .duration(500)
t1.select("path.line")
    .attr("d", "M40,40L80,80");

这是最终代码(jsfiddle):

var margin = {top: 40, bottom: 40, left: 40, right: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.bottom - margin.top;

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

svg.append("circle")
    .attr("r", 0)
    .attr("cx", 40)
    .attr("cy", 40)
    .attr("class", "point-start")

svg.append("path")
    .style("stroke", "#000")
    .style("stroke-width", 2)
    .style("fill", "none")
    .attr("class", "line")
    .attr("d", "M40,40L40,40");

svg.append("circle")
    .attr("r", 0)
    .attr("cx", 80)
    .attr("cy", 80)
    .attr("class", "point-end")

var t0 = svg.transition()
    .duration(100);

t0.select("circle.point-start")
    .attr("r", 4);

var t1 = t0.transition()
    .duration(500)
    .ease("linear");
t1.select("path.line")
    .attr("d", "M40,40L80,80");

var t2 = t1.transition()
    .duration(100);
t2.select("circle.point-end")
    .attr("r", 4);