Arduino C++将http客户端初始化移动到一个函数中。

Question

我正在做一个ESP-01 (ESP8266板)项目，并发出一些HTTP请求。我试图重构我的代码，以保持它的干燥，但我仍然停留在如何将http客户端初始化提取到一个函数上。

以下是我工作的PUT请求功能：

void httpPut(const char* url, const char* data) {
  WiFiClient client;
  HTTPClient http;

  http.begin(client, url);
  http.addHeader("Content-Type", "application/json");
  http.PUT(data);

  http.end();
}

我的想法是做一个这样的功能：

HTTPClient prepareRequest(const char* url) {
  WiFiClient client;
  HTTPClient http;

  http.begin(client, url);
  http.addHeader("Content-Type", "application/json");
  return http;
}

并在我的所有请求函数中使用，如下所示：

void httpGet(const char* url) {
  HTTPClient http = prepareRequest(url);
  http.GET();
  http.end();
}

我得到了这个编译器错误，但我不太确定它意味着什么(第90行提到的是return http;)：

/home/<user>/Code/Micro/mittari-micro/src/mittari.ino: In function 'HTTPClient prepareRequest(const char*)':
/home/<user>/Code/Micro/mittari-micro/src/mittari.ino:90:10: error: use of deleted function 'HTTPClient::HTTPClient(const HTTPClient&)'
   90 |   return http;
      |          ^~~~
In file included from /home/<user>/Code/Micro/mittari-micro/src/mittari.ino:2:
/home/<user>/.platformio/packages/framework-arduinoespressif8266/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.h:151:7: note: 'HTTPClient::HTTPClient(const HTTPClient&)' is implicitly deleted because the default definition would be ill-formed:
  151 | class HTTPClient
      |       ^~~~~~~~~~
/home/<user>/.platformio/packages/framework-arduinoespressif8266/libraries/ESP8266HTTPClient/src/ESP8266HTTPClient.h:151:7: error: use of deleted function 'std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = StreamString; _Dp = std::default_delete<StreamString>]'
In file included from /home/<user>/.platformio/packages/toolchain-xtensa/xtensa-lx106-elf/include/c++/10.3.0/memory:83,
                 from /home/<user>/.platformio/packages/framework-arduinoespressif8266/libraries/ESP8266WiFi/src/ESP8266WiFiGeneric.h:28,
                 from /home/<user>/.platformio/packages/framework-arduinoespressif8266/libraries/ESP8266WiFi/src/ESP8266WiFiSTA.h:28,
                 from /home/<user>/.platformio/packages/framework-arduinoespressif8266/libraries/ESP8266WiFi/src/ESP8266WiFi.h:34,
                 from /home/<user>/Code/Micro/mittari-micro/src/mittari.ino:1:
/home/<user>/.platformio/packages/toolchain-xtensa/xtensa-lx106-elf/include/c++/10.3.0/bits/unique_ptr.h:468:7: note: declared here
  468 |       unique_ptr(const unique_ptr&) = delete;
      |       ^~~~~~~~~~

是否有可能将通用功能提取到函数中，我如何才能做到这一点？

Answer 1

您正在尝试在HTTPClient函数的末尾按值返回一个prepareRequest对象(http)。在这种情况下，这意味着复制构造，编译器告诉您，此类的复制构造是故意禁用的。(这可能有很多原因。)

在Arduino环境中这样做通常是将"WiFiClient客户端“和"HTTPClient http”移动到全局范围。然后将您的初始化代码写入"setup“函数中，最后您可以在任何您喜欢的函数中使用它们。这样，您就可以将URL和头的设置分离到"prepareRequest“函数中--实际的http进入"httpGet”函数，而不需要它们返回任何内容。

有更复杂的解决方案，包括const引用、指针等。但除非你特别想走这条路，否则我会支持上面提到的解决方案。

Answer 2

我将WiFiClient和HTTPClient放在全局范围内，并将准备方法更改为无效，如下所示：

WiFiClient client;
HTTPClient http;

void prepareRequest(const char* url) {
  http.end(); // In case previous request did not call end for some reason.
  http.begin(client, url);
  http.addHeader("Content-Type", "application/json");
}

void httpGet(const char* url) {
  prepareRequest(url);
  http.GET();
  http.end();
}

到目前为止似乎还不错。