[英]Ionic2 function setInterval can't get a parameter
I use Ionic2 to build an app,which based on Angular2 and Cordova. 我使用Ionic2构建一个基于Angular2和Cordova的应用程序。 when I use function setInterval to get a parameter called clickCount,it occurt an undefine error.
当我使用函数setInterval来获取一个名为clickCount的参数时,它会发出一个undefine错误。
export class ItemDetailsPage {
static get parameters() {
return [[NavController], [NavParams]];
}
constructor(nav, navParams) {
this.nav = nav;
this.clickCount = 0;
this.selectedItem = navParams.get('item');
}
startTapped(event) {
var cp= this.clickCount; //here can get the clickCount
this.stop = setInterval(function() {
console.log(this.clickCount); //occur a undefined error
}, 1000);
}
} }
it is a scope problem, to solve it quickly, just do it: 这是一个范围问题,要快速解决它,就这样做:
startTapped(event) {
var that = this;
this.stop = setInterval(function() {
console.log(that.clickCount); //no more undefined error
}, 1000);
}
I happens because "this" inside the "setInterval" is the function "setInterval" it self, not the "this" of the scope of "startTapped", if you create a pointer to the "this", you can use that pointer inside "setInterval" 我发生的原因是“setInterval”里面的“this”是函数“setInterval”它自己,而不是“startTapped”范围的“this”,如果你创建一个指向“this”的指针,你可以在里面使用那个指针“的setInterval”
I don't know ionic
but I think you should use arrow function/fat arrow
as shown below, 我不知道
ionic
但我认为你应该使用arrow function/fat arrow
,如下所示,
this.stop = setInterval(()=> {
console.log(this.clickCount); //this will log this.clickCount
}, 1000);
}
You can check this answer with arrow function
and without arrow function
. 您可以使用
arrow function
和没有arrow function
来检查此答案。 But no Ionic. 但没有离子。 sorry for that.
对不起
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