Angular 8 Http Post从订阅获取布尔值

如何解决Angular 8 Http Post从订阅获取布尔值

我尝试从布尔值true / false的 subscribe 中获取价值，但是我无法获取价值，这是我到目前为止使用的内容。

我的http帖子的旧方法。

this.http.post(HostedPathConst.HostedPath + `CompanyProfile/UpdateCustomersStatus`,fData)
.subscribe(data => this.Success(data),err => this.Error(err)); 

this.Success(data)和this.Error(err)是现在被调用的方法，我尝试获取数据的新方法是这样。

const fData = new FormData();
fData.append('Id',Id.toString());    
fData.append('IsActive',IsActive.toString());
const test = this.http.post(HostedPathConst.HostedPath + `CompanyProfile/UpdateCustomersStatus`,fData)
  .subscribe(data => {
    this.Success(data);
    this.Switch = IsActive;
    return this.Switch;
  },err => {
      this.Error(err);
      this.Switch = !IsActive;
      return this.Switch;
    });
    console.log(test);//Subscriber {closed: false,_parentOrParents: null,_subscriptions: Array(1),syncErrorValue: null,syncErrorThrown: false, …}
    console.log(this.Switch);//undefined at first then gives opposite result like true gives false and vice versa

作为this.Switch = IsActive;的布尔值以获取数据，它首先返回 undefined ，然后在病房之后返回值 false 而不是 true ，反之亦然。

解决方法

因为我了解您的问题是由于异步内容，所以我将在此处写一个说明。简单地说，您不知道异步操作何时结束。例如，当您执行http函数时，您正在与服务器通信，因此您不知道服务器何时响应（由于连接速度慢，通信量大，或者可能是因为您要求繁重的操作）。 / p>

为解决此问题，我们使用了使用观察者模式的subscribe（）方法。因此，这里的要点是因为您不知道服务器或操作（如线程）何时完成，因此您订阅了该服务器并一直在观察任何更改或答案。收到该消息后，将执行订阅中的代码。

您可以在此处了解有关观察者模式的更多信息：https://en.wikipedia.org/wiki/Observer_pattern#:~:text=The%20observer%20pattern%20is%20a,calling%20one%20of%20their%20methods。 和异步理论在这里：https://en.wikipedia.org/wiki/Asynchrony_(computer_programming)

对于您的问题，您可以将值初始化为false，并将复选框值设置为[（ngModel）] =“ Switch”，以便在更新开关变量时，复选框也将更新！

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由于其可观察，因此您不会立即得到响应。因此控制台记录此内容。在成功和错误块内切换。尝试以下代码段

const fData = new FormData();
fData.append('Id',Id.toString());    
fData.append('IsActive',IsActive.toString());
const test = this.http.post(HostedPathConst.HostedPath + `CompanyProfile/UpdateCustomersStatus`,fData)
  .subscribe(data => {
    this.Success(data);
    this.Switch = IsActive;
    console.log("Success",this.Switch);
    return this.Switch;
  },err => {
      this.Error(err);
      this.Switch = !IsActive;
      console.log("Error",this.Switch);
      return this.Switch;
    });

我不确定这是否可以解决您的问题，但是绝对可以通过调试来获取解决方案。

注意：您得到undefined at first then gives opposite result like true gives false and vice versa的原因是，您在成功或错误块之外安慰this.Switch，这在大多数情况下都会首先返回undefined，接下来分配值。由于this.Switch是全局作用域变量。

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使用def parse_competitor_product_page(self,response): # Function that scrapes information from a product page and yields the competitor # only if it actually matches our search. ' Do some work and scrape required product attributes' competitor = ProductItem() competitor['product'] = prod_name competitor['asin'] = asin competitor['Title'] = title competitor['producer'] = producer competitor['MainImage'] = image competitor['Rating'] = rating competitor['NumberOfReviews'] = number_of_reviews competitor['price'] = price competitor['AvailableSizes'] = sizes competitor['AvailableColors'] = colors competitor['Varieties'] = varieties competitor['BulletPoints'] = bullet_points competitor['SellerRank'] = seller_rank variaton = self.is_right_product(prod,competitor): if variation is True or variation is None: # send to Scarpy's Engine: ProductItem without changes yield competitor else: # send to Scarpy's Engine: Request to page with variation yield self.update_product_to_right_variation(competitor,variation) def is_right_product(self,product,competitor): # Function that checks whether a resulting competitor actually matches the product that # we looked for. It returns a boolean if it does. It also alters some attributes of that # competitor if a right variation is found on its page. '''I will omit some if else branches as those work well and I will only post the faulty branch (which happens to be the one that should modify the competitor object because a right variation is found on its page. ''' if product_is_right_quantity(competitor): return True # it will assing `True` to `variaton = ...` in `parse_competitor_product_page()` # it will assing `variation` or `None` to `variaton = ...` in `parse_competitor_product_page()` return find_variation_of_right_quantity(product['quantity'],competitor) def update_product_to_right_variation(self,competitor,variation_asin): print("IN UPDATE PRODUCT TO RIGHT VARIATION") variation_asin = response.xpath(f'//div[@id="variation_color_name"]/ul/li[contains(@title,\'{variation_name}\')]/@data-defaultasin').get() product_url = f"https://www.amazon.it/dp/{variation_asin}" print(product_url) # send back to `parse_competitor_product_page()` return scrapy.Request(url=product_url,callback=self.update_competitor_from_product_page,errback=self.errback_http,meta={'prod':competitor,'asin':variation_asin}) def update_competitor_from_product_page(self,response): print("INSIIDE UPDATE COMPETITOR FROM PRODUCT PAGE") prod = response.meta['prod'] asin = response.meta['asin'] price = response.xpath('//*[@id="priceblock_ourprice"]/text()').extract_first() #title = ... prod['price'] = price prod['Title'] = title prod['asin'] = asin #response.meta['prod'] = prod # useless print(prod['price']) # send to Scarpy's Engine: item with changes yield prod 和async来获得结果并且有效。

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