如何在D3中重用两个(或更多)链式转换序列

Question

我必须应用两个很长的链式转换序列,它们主要区别于转换的顺序,我正在寻找一种紧凑的代码方式.

作为一个玩具例如,考虑顺序订单应该是这样的a,b,c,d,e,f,g,h和e,f,g,h,a,b,c,d.我已尝试使用下面的代码,但它不起作用.请注意,转换可能有不同的属性(delay,duration,ease,等等),他们可以适用于不同的属性(x,y,width,height或cx,cy,r,等)和样式.例如,转换a可以参考width,过渡b到height,过渡c到x,过渡d到y,过渡e到transform属性,过渡f到color风格,等等.

PS:这个问题与我之前的问题具有相同的目的,但在那里我使用了太多简单的编码案例,误导了答案.

有没有办法以紧凑的方式编码？

var t1 = d3
.transition() // transition "a" specifications 
...
.transition() // transition "b" specifications 
...
.transition() // transition "c" specifications 
...
.transition() // transition "d" specifications 
...
;
var t2 = d3
.transition() // transition "e" specifications 
...
.transition() // transition "f" specifications 
...
.transition() // transition "g" specifications 
...
.transition() // transition "h" specifications 
...
;
someelement1
.transition(t1).transition(t2); 
someelement2
.transition(t2).transition(t1); 

Answer 1

如评论中所述,回答此问题的原则与您之前的问题相同.在这种情况下,您有一组不同的转换,可以按不同键引用的任何顺序应用.让我们将它们存储在一个对象中:

var transitions = {
  a: function(sel){ return sel.transition().duration(1000).delay(1000).attr('cy', 200) },
  b: function(sel){ return sel.transition().duration(2000).delay(0).attr('r', 40) },
  c: function(sel){ return sel.transition().duration(500).delay(1500).attr('fill', 'red') },
  d: function(sel){ return sel.transition().duration(1500).delay(500).attr('opacity', 0.5) },
  e: function(sel){ return sel.transition().duration(1000).delay(3000).attr('cy', 300) },
  f: function(sel){ return sel.transition().duration(2000).delay(0).attr('r', 60) },
  g: function(sel){ return sel.transition().duration(500).delay(1500).attr('fill', 'magenta') },
  h: function(sel){ return sel.transition().duration(1500).delay(500).attr('opacity', 0.25) }
};

每个函数都接受一个d3.selection对象,并将特定的转换参数和转换集应用于它.这些功能可以随心所欲地变长和复杂.我很懒,想象力很少,所以他们只在这个版本中进行一次转换.

这里已经有一些代码重复,所以让我们将选择转换为转换,并使用this而不是传递参数:

var transitions = {
  a: function(){ return this.duration(1000).delay(1000).attr('cy', 200) },
  b: function(){ return this.duration(2000).delay(0).attr('r', 40) },
  c: function(){ return this.duration(500).delay(1500).attr('fill', 'red') },
  d: function(){ return this.duration(1500).delay(500).attr('opacity', 0.5) },
  e: function(){ return this.duration(1000).delay(3000).attr('cy', 300) },
  f: function(){ return this.duration(2000).delay(0).attr('r', 60) },
  g: function(){ return this.duration(500).delay(1500).attr('fill', 'magenta') },
  h: function(){ return this.duration(1500).delay(500).attr('opacity', 0.25) }
};

现在我们可以通过调用代码来执行这些转换

transitions['a'].call( selection.transition() )
transitions.f.call( d3.select('circle').transition() )

您想要指定要应用于选择的过渡数组,如下所示:

apply_transitions( group.select(":nth-child(1)"), ['a','b','c','d'] );
apply_transitions( group.select(":nth-child(2)"), ['e','f','g','h'] );

这可以实现如下:

/**
* apply a series of transitions to a selection
*
* @param selection - d3 selection
* @param tr_arr - array of transition identifiers, referring to functions in the `transitions` object
*/
function apply_transitions( selection, tr_arr ) {

  // turn the current selection into a d3.transition
  // call the transition function referred to by the first ID in the array
  // with the d3.transition as the `this` context
  // note that the function returns a transition object, so it can be chained
  transitions[ tr_arr[0] ].call( selection.transition() )
  // add a handler to be applied at the end of the transition
    .on('end', function(){
      // if there are more transitions to be applied, call
      // apply_transitions again with tr_arr minus the first element
      // note that the `this` context in the `on` function is a DOM element,
      // so use `d3.select(this)` to turn it into a d3 selection
      if ( tr_arr.length > 1 ) {
        apply_transitions( d3.select(this), tr_arr.slice(1) );
      }
    })
}

实时动作示例:

    var svg = d3.select('svg').attr('width', 500).attr('height', 500);

    var dataSet = [20, 20];

    var group=svg.append("g");
    var circles = group.selectAll('circle')
    .data(dataSet)
    .enter()
    .append('circle')
    .attr("r",function(d){ return d })
    .attr("cx",function(d, i){ return i * 100 + 50 })
    .attr("cy",50)
    .attr("fill",'black');

    apply_transitions( group.select(":nth-child(1)"), ['a','b','c','d'] );

    apply_transitions( group.select(":nth-child(2)"), ['e','f','g','h'] );

  function apply_transitions( selection, tr_arr ) {

    var transitions = {
      a: function(){ return this.duration(1000).delay(1000).attr('cy', 200) },
      b: function(){ return this.duration(2000).delay(0).attr('r', 40) },
      c: function(){ return this.duration(500).delay(1500).attr('fill', 'red') },
      d: function(){ return this.duration(1500).delay(500).attr('opacity', 0.5) },
      e: function(){ return this.duration(1000).delay(3000).attr('cy', 300) },
      f: function(){ return this.duration(2000).delay(0).attr('r', 60) },
      g: function(){ return this.duration(500).delay(1500).attr('fill', 'magenta') },
      h: function(){ return this.duration(1500).delay(500).attr('opacity', 0.25) }
    };

      transitions[ tr_arr[0] ].call( selection.transition() )
        .on('end', function(){
          if ( tr_arr.length > 1 ) {
            apply_transitions( d3.select(this), tr_arr.slice(1) );
          }
        })
  }

<script src="http://d3js.org/d3.v5.js"></script>
<svg></svg>