Javascript:从嵌套函数调用外部方法

Question

这个问题已经有答案了:

How to access the correct `this` inside a callback (15 个回答)

已关闭 4 年前。

我要调用openSnackBar但我得到异常(exception)。任何人都可以帮助我如何处理嵌套函数的外部方法调用？

export class DetailsComponent implements OnInit, OnDestroy
{
updateTodoPromise.then(function (fulfilled) {
            // yay, you got a new phone
            this.openSnackBar('Task saved successfully!', 'CLOSE');
        })
        .catch(function (error) {
            // ops, mom don't buy it
            console.log(error.message);
            this.openSnackBar('Task saved successfully!','CLOSE');
        });

    }

    public openSnackBar(full: string, full2: string) {
        this.snackBar.open(full, full2, {
            duration: 5000,
        });
    }

Answer 1

使用 ES6 双箭头表示法来保留 this 范围。

export class DetailsComponent implements OnInit, OnDestroy
{
updateTodoPromise.then( fulfilled => { // <--- here
            // yay, you got a new phone
            this.openSnackBar('Task saved successfully!', 'CLOSE');
        })
        .catch( error => {  // <--- and here
            // ops, mom don't buy it
            console.log(error.message);
            this.openSnackBar('Task saved successfully!','CLOSE');
        });

    }

    public openSnackBar(full: string, full2: string) {
        this.snackBar.open(full, full2, {
            duration: 5000,
        });
    }