Add support for dynamic text

[jonathancounihan]

Add the ability for the label text to be created via a function, to support dynamically changing text.

[jonathancounihan]

Pull request #6 fixes this issue.

[ciprianciurea]

Fixes #6 , #5

[jonathancounihan]

sure @ciprianciurea, will do so. The basic one I can think of is when the legend is displayed and you toggle a segments visibility as shown here:

The relevant code, using the changes I made:

text: function() {
  var total = cht.config.data.datasets[0]._meta[0].total;
  return total;
},

[ciprianciurea]

Thanks @jonathancounihan , managed to update the samples in the meantime.

[JohnArcher]

The code @jonathancounihan posted does not work here (chart.js 2.8.0). _meta[0] is not defined. I had to use this: chart.data.datasets[0]._meta[Object.keys(theChart.data.datasets[0]._meta)[0]].total

My other problem with your example is that I have no access to cht in this scope in my project. So I would like to do a PR which passes the chart object to the text() function (similar to other Chart.js plugins).

[JohnArcher]

You'll find my PR here: #11

[JohnArcher]

As I had several trouble using the internal _meta property you should not use this. As stated in https://github.com/chartjs/Chart.js/issues/4731#issuecomment-328279321 you should use getDatasetMeta () instead.

[vasyl-shumskyi]

chart.getDatasetMeta(0).total works nicely

[Eduardops4]

Add the ability for the label text to be created via a function, to support dynamically changing text.

Olá boa noite