Issue
I have a very simple class, but already run into pain with the definition of ‘this’ in Typescript:
Typescript
/// <reference path='jquery.d.ts' />
/// <reference path='bootstrap.d.ts' />
module Problem {
export class Index {
detailsUrl: string;
constructor() {
$('.problem-detail-button').click((e) => {
e.preventDefault();
var $row = $(this).closest('tr'); //this must be that of the callback
var problemId: number = $row.data('problem-id');
$.ajax({
url: this.detailsUrl, //this must be the instance of the class
data: { id: problemId },
type: 'POST',
success: (result) => {
$('#details-modal-placeholder').html(result);
$('#details-modal-placeholder modal').modal('show');
},
})
});
}
}
}
Javascript
var Problem;
(function (Problem) {
var Index = (function () {
function Index() {
var _this = this;
$('.problem-detail-button').click(function (e) {
e.preventDefault();
var $row = $(_this).closest('tr');
var problemId = $row.data('problem-id');
$.ajax({
url: _this.detailsUrl,
data: {
id: problemId
},
type: 'POST',
success: function (result) {
$('#details-modal-placeholder').html(result);
$('#details-modal-placeholder modal').modal('show');
}
});
});
}
return Index;
})();
Problem.Index = Index;
})(Problem || (Problem = {}));
Now the problem is that the line
var $row = $(this).closest('tr'); //this must be that of the callback
and this line
this.detailsUrl, //this must be the instance of the class
conflict in the meaning of 'this'
How do you handle the mixture of the 'this'?
Solution
module Problem {
export class Index {
detailsUrl: string;
constructor() {
var that = this;
$('.problem-detail-button').click(function (e) {
e.preventDefault();
var $row = $(this).closest('tr'); //this must be that of the callback
var problemId: number = $row.data('problem-id');
$.ajax({
url: that.detailsUrl, //this must be the instance of the class
data: { id: problemId },
type: 'POST',
success: (result) => {
$('#details-modal-placeholder').html(result);
$('#details-modal-placeholder modal').modal('show');
},
})
});
}
}
}
Explicitly declare that = this
so you have a reference for that.detailsUrl
, then
don't use a fat arrow for the click handler, so you get the correct this
scope for the callback.
Answered By - Jude Fisher
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