D3 v4 - 无法读取null的属性文本 [英] D3 v4 - cannot read property text of null

问题描述

我一直在尝试转换一个漂亮的D3图表示例（ https://jsfiddle.net/thudfactor/

I've been trying to convert a nice D3 chart example ( https://jsfiddle.net/thudfactor/HdwTH/ ) to an Angular2 component with the new D3 v4.

但我得到一个无法读取属性文本的null异常与以下代码：

I do however get a "cannot read property text of null" exception with the following code:

var textLabels = labelGroups.append("text").attr({
    x: function (d, i) {
        var centroid = pied_arc.centroid(d);
        var midAngle = Math.atan2(centroid[1], centroid[0]);
        var x = Math.cos(midAngle) * cDim.labelRadius;
        var sign = (x > 0) ? 1 : -1
        var labelX = x + (5 * sign)
        return labelX;
    },
    y: function (d, i) {
        var centroid = pied_arc.centroid(d);
        var midAngle = Math.atan2(centroid[1], centroid[0]);
        var y = Math.sin(midAngle) * cDim.labelRadius;
        return y;
    },
    'text-anchor': function (d, i) {
        var centroid = pied_arc.centroid(d);
        var midAngle = Math.atan2(centroid[1], centroid[0]);
        var x = Math.cos(midAngle) * cDim.labelRadius;
        return (x > 0) ? "start" : "end";
    },
    'class': 'label-text'
}).text(function (d, i) {      <--------------- exception
    return d.data.label;
});

labelgroups是一个选择，append应该工作，所以它必须是。 attr（{}）导致问题。但是它在jsfiddle中工作正常。

D3 v4中的语法有没有改变？

labelgroups is a selection, append should work, so it must be the .attr({}) causing the problem. It does however work fine in the jsfiddle.
Has this syntax changed in D3 v4? How would it be correct?

谢谢！

推荐答案

新的D3 v4.x，您不能使用对象来设置 attr 或 style 。要这样做，你必须引用迷你库D3-selection-multi：

In the new D3 v4.x, you cannot use objects to set attr or style. To do so, you have to reference the mini library D3-selection-multi:

<script src="https://d3js.org/d3-selection-multi.v0.4.min.js"></script>

$ b > attrs （是的，复数形式）：

After doing that, change your code from attr to attrs (yes, like a plural):

var textLabels = labelGroups.append("text").attrs({
    //all the key-value pairs here
});

对样式执行相同操作： styles 作为复数，不是 style 。

Do the same for the styles: it should be styles, as a plural, not style.

如果您不想更改所有这些，简单地做为常规方式：set x ， y ， text-anchor 和和在 attr 中。

If you don't want to change all this, simply do as the "regular" way: set x, y, text-anchor and class in separate attr.

这是 selection-multi 文档： https://github.com/d3/d3-selection-multi/blob/master/README.md#selection_attrs

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