Scope of this is lost when passing a member function to setInterval
#10.285 aperta il 11 ago 2016
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Descrizione
TypeScript Version: 1.8.10
When passing a member function to setInterval, the scope of 'this' is lost within the callback, though the structure of the code (given experience of any object orientated language) indicates it shouldn't be.
Example code
export class SetIntervalTest {
private someNumber: number = 1;
trigger() {
setInterval(this.setIntervalCallback, 400);
}
private setIntervalCallback() {
console.log(this.someNumber);
}
}
Expected behavior When console.log(this.someNumber); is called, the scope of this is within the scope of the SetIntervalTest interval instance, printing '1'.
Actual behavior: The scope of this is pulled from global scope, resulting in this.someNumber being 'undefined'. If that isn't possible, the compiler should indicate the expected behaviour is not what you're going to get.
To fix this i need to change 'setInterval(this.setIntervalCallback, 400);' to 'setInterval(() => this.setIntervalCallback(), 400);' so 'this' is correctly scoped in the callback.