Update chart.js after form submission and page reload - ajax

Question

I have a chart.js bar chart that pulls data via an ajax call to a Django APIView. The ajax call returns one dictionary with a stack of data inside I use to customize the chart. Here's the chart.js code:
var current_year = '{% url "saveskore:api-current-year-savings" %}'
$.ajax({
url: current_year,
type: 'GET',
cache: false,
dataType: 'json',
success: function(data) {
var ctx = document.getElementById('current-year-chart');
var chart = new Chart(ctx, {
type: 'bar',
data: {
labels: data['dates'],
datasets: [
{
label: data['income_label'],
backgroundColor: "#8e5ea2",
data: data['income'],
},
{
label: data['expense_label'],
backgroundColor: 'green',
data: data['expenses'],
},
{
label: data['savings_label'],
backgroundColor: "#3e95cd",
data: data['savings_goal'],
},
{
label: data['avail_label'],
backgroundColor: "#pink",
data: data['avail_to_spend'],
},
]
},
options: {
legend: { display: false },
title: {
display: true,
text: 'Savings for ' + data['year']
}
}
});
}
});
Works great. Looks great.
But! I have a django formset on a separate page that updates the table data that the chart pulls from.
When I update the data in the formset and submit, redirecting to the chart page ... NO UPDATE OCCURS.
If I make some code change or otherwise reload the browser, VOILA, the chart updates.
I have read about either cache=false and chart.update(), but find i have not been able to make either work, mainly because the exact details on their use are not clear.
I would really appreciate input on this.

Answer 1

Have you tried chart.destroy() method ? and then build again the chart with the new data .. that works for me.. take a look at my example
let flag = 0;
var xChart = "";
function dibujar(valor, meses) {
try {
if (valor.length > 0) {
$('#grafico').fadeIn('fast');
var canvas = document.getElementById('chart');
let tipGra = $('#slcTipGra').val();
if (flag !== 0) {
xChart.destroy();
}
//rgba(54, 162, 235, 0.2)
if (tipGra === "bar" || tipGra === "horizontalBar") {
var data = {
labels: meses,
datasets: [
{
label: "Dólares($)",
backgroundColor: "#3e95cd",
borderColor: "#3e95cd",
borderWidth: 2,
hoverBackgroundColor: "#3e95cd",
hoverBorderColor: "#3e95cd",
data: valor,
}
]
};
var option = {
title: {
display: true,
fontSize: 20,
fontFamily: 'Helvetica',
text: 'Reporte Mensual de Ventas'
},
plugins: {
datalabels: {
color: 'white',
anchor: 'end',
align: 'start',
font:
{
weight: 'bold'
}
}
},
scales: {
yAxes: [{
stacked: true,
gridLines:
{
display: true,
color: "rgba(255,99,132,0.2)"
}
}],
xAxes: [{
gridLines: {
display: true
}
}]
}
};
}
if (tipGra === 'line') {
var data = {
labels: meses,
datasets: [
{
label: "Dólares($)",
fill: false,
lineTension: 0.1,
backgroundColor: "rgba(75,192,192,0.4)",
borderColor: "rgba(75,192,192,1)",
borderCapStyle: 'butt',
borderDash: [],
borderDashOffset: 0.0,
borderJoinStyle: 'miter',
pointBorderColor: "rgba(75,192,192,1)",
pointBackgroundColor: "#fff",
pointBorderWidth: 1,
pointHoverRadius: 5,
pointHoverBackgroundColor: "rgba(75,192,192,1)",
pointHoverBorderColor: "rgba(220,220,220,1)",
pointHoverBorderWidth: 2,
pointRadius: 5,
pointHitRadius: 10,
data: valor,
}
]
};
var option = {
title: {
display: true,
fontSize: 20,
fontFamily: 'Helvetica',
text: 'Reporte Mensual de Ventas'
},
plugins: {
datalabels: {
backgroundColor: function (context) {
return context.dataset.borderColor;
},
borderRadius: 4,
color: 'white',
anchor: 'end',
align: 'end',
}
},
showLines: true
};
}
xChart = new Chart(canvas,
{
type: tipGra,
data: data,
options: option
});
flag = 1;
}
else {
$('#grafico').fadeOut('fast');
$('#graficoMessage').fadeIn('slow');
}
} catch (err) {
console.log(err);
}
}
I declare "xChart" as a global variable and a flag to know if it's the first chart to build. The example build 3 different types of charts (Vertical Bar, Horizontal Bar and Line) depending on the selection of the chart type "let tipGra = "$('#slcTipGra').val();"