vue Cannot read property 'get' of undefined

vue Cannot read property 'get' of undefined

Except for forgetting to introduce vue-resource 

It may also be that the directionality of this has changed

handleDel:function(id){
    let that = this;
    parent.layer.confirm('Are you sure to delete?', {
        btn: ['Confirm','Cancel'], 
        shade: false //Do not display the mask
    }, function() {
        //confirm
        that.$http.get("/position/delete/"+id).then(function(res){
            if(res.data.action){
                parent.layer.msg(res.data.msg);
                this.getList(1);
            }else{
                parent.layer.msg(res.data.msg);
            }
        })
    })
}