小编bca*_*cap的帖子

构建一个小型反应应用程序,通过地理定位(由浏览器确定为子组件作为道具).

第一个组件:App.jsx

import React, {Component} from 'react';

import DateTime from './components/dateTime/_dateTime.jsx';
import Weather from './components/weather/_weather.jsx';
import Welcome from './components/welcome/_welcome.jsx';

require ('../sass/index.scss');

export default class App extends Component {

  constructor() {
    super();
    this.state = {
      latitude: '',
      longitude: ''
    };
    this.showPosition = this.showPosition.bind(this);
  }

  startApp () {
    this.getLocation();
  }

  getLocation() {
    if (navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(this.showPosition);
    } else {
        console.log("Geolocation is not supported by this browser.");
    }
  }

  showPosition(position) {
    this.setState({
        latitude: position.coords.latitude,
        longitude: position.coords.longitude
    })
  }

  componentWillMount () {
    this.startApp();
  } …

我有类Invoice,其中(简化)具有以下属性:

class Invoice(models.Model)
    number = models.CharField(verbose_name="Number", max_length=16)
    issue_date = models.DateTimeField(verbose_name="Issue date", default=datetime.now)
    total = models.FloatField(verbose_name="Total", blank=True, null=True)

然后,我有InvoiceLine类,它代表发票可以拥有的行/行:

class InvoiceLine(models.Model):
    invoice = models.ForeignKey(Invoice, verbose_name="Invoice")
    description = models.CharField(verbose_name="Description", max_length=64)
    line_total = models.FloatField(verbose_name="Line total")

InvoiceLine是Invoice的内联,我想要实现的是,当在管理员中有人用发票线(一个或多个)保存发票时,计算发票总额.我试图通过覆盖方法保存来做到这一点:

class Invoice(models.Model)
    number = models.CharField(verbose_name="Number", max_length=16)
    issue_date = models.DateTimeField(verbose_name="Issue date", default=datetime.now)
    total = models.FloatField(verbose_name="Total", blank=True, null=True)

    def save(self, *args, **kwargs):
         invoice_lines = InvoiceLine.objects.filter(invoice=self.id)
         self.total = 0
         for line in invoice_lines:
             self.total=self.total+line.line_total
         super(Invoice, self).save(*args, **kwargs)

问题是,当我在InvoiceLine中添加元素时,第一次保存并调用functionsave时,内联(InvoiceLine)中的新元素尚未存储,所以当我这样做时InvoiceLine.objects.filter(invoice=self.id),它们不会被考虑在内.因此,这种方法的唯一方法是节省两次.我也尝试过:

def save(self, *args, **kwargs):
    super(Invoice, self).save(*args, **kwargs)
    invoice_lines = InvoiceLine.objects.filter(invoice=self.pk) …