angular2在构造函数中创建一个变量

Question

我想在构造函数(或函数)中创建一个变量。我不想在全班创造。这有可能吗？

这是我的密码

import { Component, OnInit } from '@angular/core';
import { FormGroup, FormBuilder, Validators } from '@angular/forms';
import { CustomValidators } from 'ng2-validation';
import { TranslatorService } from '../../../../core/translator/translator.service';
import { CarBrandService } from '../car-brand.service';
import { Response } from '../../../../shared/models/response';
import { SessionService } from '../../../../shared/services/session/session.service';
import { ServerService } from '../../../../shared/services/server/server.service';
import { ToasterService, ToasterConfig } from 'angular2-toaster/angular2-toaster';
import { Router } from '@angular/router';
import { CarBrand } from '../car-brand';
import { SharedModule } from '../../../../shared/shared.module';
import { Table } from '../../../../shared/models/table';
import { TableRow } from '../../../../shared/models/table-row';
import { TableAction } from '../../../../shared/models/table-action';
import { ListTableComponent } from '../../../../shared/components/list-table/list-table.component';

@Component({
  selector: 'car-brand-index',
  templateUrl: './index.component.html',
  styleUrls: ['./index.component.scss'],
  providers: [CarBrandService, Response, SessionService, ServerService,             ListTableComponent, TableAction, Table, TableRow]
})
export class CarBrandIndexComponent implements OnInit {
  error : String;
  total : number;
  items : Array<CarBrand>;
  table : Table;
  constructor(public translator: TranslatorService, private mainService : CarBrandService, public sessionService : SessionService, public response : Response, private toasterService: ToasterService, private router: Router) {

    var action : TableAction;
    action.value = "/view/";
    action.type = "link";
    this.table.actions.push(action);
    var action : TableAction;
    action.value = "/edit/";
    action.type = "link";
    this.table.actions.push(action);
    this.table.columns = ["MODULES.COMMON.LOGO", "MODULES.COMMON.NAME", "MODULES.COMMON.ACTIONS"];    
    this.getItems(1,10);
  }

  getItems(pageNumber : number, pageSize : number){
//Do something
            });        
        }
        else
          this.error = result.code;
    });
  }
  ngOnInit() {
       }
}

我是TableAction

export class TableAction {
    type : String;
    value : String;
    name : String;
    icon : String;
}

但是在下面的var操作中: TableAction；它告诉我操作是未定义的。有没有一种方法可以修复这个问题，而不需要声明类下面的var？

Answer 1

var action : TableAction；您只需告诉'action‘类型。现在，如果您试图将类似于{a: 1，b: 2} -您将看到一个错误分配给操作。

但是，如果您编写var操作: TableAction =新的TableAction() --您将根据需要在您的作用域中(contructor/function)中有一个实例，并为变量' action‘定义一个类型。

建议:使用let而不是var

let action = new TableAction(); 

使用关键字'let‘定义的变量的行为更可预测。

constructor() {
  let action1 = new TableAction("/view/", "link");
  this.table.actions.push(action1);

  let action2 = new TableAction("/edit/", "link");
  this.table.actions.push(action2);
  // ...
}

export class TableAction {
  type : String;
  value : String;
  name : String;
  icon: String;

  constructor(value, type) { 
    this.value = value;
    this.type = type;
  }
}

Answer 2

var action : TableAction

是一份声明。

var action : TableAction=new TableAction();

或

var action : TableAction = {};

是一个定义。您正在尝试设置未定义的action的对象属性。