JSON : Placeholder

JSON : Placeholder (https://jsonplaceholder.typicode.com/) 是一个用于测试的 REST API 网站。

以下使用 Task API/Rx.NET + Json.NET 调用该网站的 REST API，获取字符串以及 JSON 数据。

• GET /posts/1
• GET /posts
• POST /posts
• PUT /posts/1
• DELETE /posts/1

所有 GET API 都返回JSON数据，格式（JSON-Schema）如下：

{

  "type":"object",

  "properties": {

    "userId": {"type" : "integer"},

    "id": {"type" : "integer"},

    "title": {"type" : "string"},

    "body": {"type" : "string"}

  }

}

安装 C++ REST SDK

$ brew install cpprestsdk

$ brew install boost

$ brew install libressl

安装 "JSON for Modern C++"

$ brew tap nlohmann/json

$ brew install nlohmann_json

下载 RxCpp

$ git clone --recursive https://github.com/ReactiveX/RxCpp.git

创建工程

打开 Xcode，File / New / Project...

在向导的第1页选 macOS / Command Line Tool

在向导的第2页语言选 C++，Product Name 填上任意名称

在向导的第3页选择任意文件夹，点击 Create 创建工程。

配置工程

将 System Header Search Paths 设置为

/usr/local/Cellar/cpprestsdk/2.10.2/include

/usr/local/Cellar/boost/1.67.0_1/include

/usr/local/Cellar/libressl/2.7.4/include

/usr/local/Cellar/nlohmann_json/3.1.2/include

RxCpp安装文件夹/Rx/v2/src

将 Library Search Paths 设置为

/usr/local/Cellar/cpprestsdk/2.10.2/lib

/usr/local/Cellar/boost/1.67.0_1/lib

/usr/local/Cellar/libressl/2.7.4/lib

将 Other Linker Flags 设置为

-lcpprest -lboost_system -lboost_thread-mt -lboost_chrono-mt -lssl -lcrypto

cpprestsdk: Undefined symbols for architecture x86_64

Post

在工程中添加 post.hpp，内容如下

#ifndef Post_hpp

#define Post_hpp

#include <iostream>

#include <nlohmann/json.hpp>

using nlohmann::json;

struct Post {

    int userId;

    int id;

    std::string title;

    std::string body;

};

void to_json(json& j, const Post& p);

void from_json(const json& j, Post& p);

std::ostream& operator<<(std::ostream& out, const Post& p);

#endif /* Post_hpp */

在工程中添加 post.cpp，内容如下

#include "Post.hpp"

#include <boost/algorithm/string/replace.hpp>

using namespace std;

void to_json(json& j, const Post& p) {

    j = json{{"userId", p.userId}, {"id", p.id}, {"title", p.title}, {"body", p.body}};

}

void from_json(const json& j, Post& p) {

    p.userId = j.at("userId").get<int>();

    p.id = j.at("id").get<int>();

    p.title = j.at("title").get<string>();

    p.body = boost::algorithm::replace_all_copy(j.at("body").get<string>(), "\n", "\\n");

}

std::ostream& operator<<(std::ostream& out, const Post& p) {

    cout << "Post {userId = " << p.userId

        << ", id = " << p.id

        << ", title = \"" << p.title

        << "\", body = \"" << p.body

        << "\"}";

    return out;

}

RestApi

在工程中添加 RestApi.hpp，内容如下

#ifndef RestApi_hpp

#define RestApi_hpp

#include <cpprest/http_client.h>

#include <cpprest/filestream.h>

#include <cpprest/json.h>

using namespace utility;                    // Common utilities like string conversions

//using namespace web;                        // Common features like URIs.

using namespace web::http;                  // Common HTTP functionality

using namespace web::http::client;          // HTTP client features

using namespace concurrency::streams;       // Asynchronous streams

#include "rxcpp/rx.hpp"

namespace Rx {

    using namespace rxcpp;

    using namespace rxcpp::sources;

    using namespace rxcpp::operators;

    using namespace rxcpp::util;

}

using namespace Rx;

#include <nlohmann/json.hpp>

using nlohmann::json;

template<class T>

struct RestApi {

    http_client client;

    RestApi(const uri &base_uri) : client(base_uri) {}

    observable<string_t> getString(const string_t &path_query_fragment) {

        return observable<>::create<string_t>(

        [&](subscriber<string_t> s){

            client

            .request(methods::GET, path_query_fragment)

            .then([](http_response response) -> pplx::task<string_t> {

                return response.extract_string();

            })

            .then([&](pplx::task<string_t> previousTask) {

                try {

                    string_t const & v = previousTask.get();

                    s.on_next(v);

                    s.on_completed();

                } catch (http_exception const & e) {

                    s.on_error(std::current_exception());

                }

            })

            .wait();

        });

    }

    observable<T> getObject(const string_t &path_query_fragment) {

        return observable<>::create<T>(

        [&](subscriber<T> s){

            client

            .request(methods::GET, path_query_fragment)

            .then([](http_response response) -> pplx::task<string_t> {

                return response.extract_string();

            })

            .then([&](pplx::task<string_t> previousTask) {

                try {

                    string_t const & v = previousTask.get();

                    json j = json::parse(v);

                    T t = j;

                    s.on_next(t);

                    s.on_completed();

                } catch (http_exception const & e) {

                    s.on_error(std::current_exception());

                }

            })

            .wait();

        });

    }

    observable<T> getArray(const string_t &path_query_fragment) {

        return observable<>::create<T>(

        [&](subscriber<T> s){

            client

            .request(methods::GET, path_query_fragment)

            .then([](http_response response) -> pplx::task<string_t> {

                return response.extract_string();

            })

            .then([&](pplx::task<string_t> previousTask) {

                try {

                    string_t const & v = previousTask.get();

                    json j = json::parse(v);

                    std::vector<T> vec = j;

                    for(const auto& t : vec)

                        s.on_next(t);

                    s.on_completed();

                } catch (http_exception const & e) {

                    s.on_error(std::current_exception());

                }

            })

            .wait();

        });

    }

    observable<string_t> createObject(const string_t& url, const T& obj) {

        return observable<>::create<string_t>(

        [&](subscriber<string_t> s){

            json j = obj;

            client

            .request(methods::POST, url, j.dump(), U("application/json"))

            .then([](http_response response) -> pplx::task<string_t> {

                return response.extract_string();

            })

            .then([&](pplx::task<string_t> previousTask) {

                try {

                    string_t const & v = previousTask.get();

                    s.on_next(v);

                    s.on_completed();

                } catch (http_exception const & e) {

                    s.on_error(std::current_exception());

                }

            })

            .wait();

        });

    }

    observable<string_t> updateObject(const string_t& url, const T& obj) {

        return observable<>::create<string_t>(

        [&](subscriber<string_t> s){

            json j = obj;

            client

            .request(methods::PUT, url, j.dump(), U("application/json"))

            .then([](http_response response) -> pplx::task<string_t> {

                return response.extract_string();

            })

            .then([&](pplx::task<string_t> previousTask) {

                try {

                    string_t const & v = previousTask.get();

                    s.on_next(v);

                    s.on_completed();

                } catch (http_exception const & e) {

                    s.on_error(std::current_exception());

                }

            })

            .wait();

        });

    }

    observable<string_t> deleteObject(const string_t& url) {

        return observable<>::create<string_t>(

        [&](subscriber<string_t> s){

            client

            .request(methods::DEL, url)

            .then([](http_response response) -> pplx::task<string_t> {

                return response.extract_string();

            })

            .then([&](pplx::task<string_t> previousTask) {

                try {

                    string_t const & v = previousTask.get();

                    s.on_next(v);

                    s.on_completed();

                } catch (http_exception const & e) {

                    s.on_error(std::current_exception());

                }

            })

            .wait();

        });

    }

};

#endif /* RestApi_hpp */

main

将 main.cpp 的内容改为

#include "Post.hpp"

#include "RestApi.hpp"

using namespace std;

int main(int argc, char* argv[])

{

    RestApi<Post> api(U("https://jsonplaceholder.typicode.com/"));

    api.getString(U("posts/1")).subscribe([](const string_t& v){cout << v << endl;});

    api.getObject(U("posts/1")).subscribe([](const Post& v){cout << v << endl;});

    api.getArray(U("posts")).take(2).subscribe([](const Post& v){cout << v << endl;});

    Post o;

    o.id = 0;

    o.userId = 101;

    o.title = U("test title");

    o.body = U("test body");

    api.createObject(U("posts"), o).subscribe([](string_t v){cout << v << endl;});

    api.updateObject(U("posts/1"), o).subscribe([](string_t v){cout << v << endl;});

    api.deleteObject(U("posts/1")).subscribe([](string_t v){cout << v << endl;});

    return 0;

}

输出结果

{

  "userId": 1,

  "id": 1,

  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",

  "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"

}

Post {userId = 1, id = 1, title = "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", body = "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"}

Post {userId = 1, id = 1, title = "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", body = "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"}

Post {userId = 1, id = 2, title = "qui est esse", body = "est rerum tempore vitae\nsequi sint nihil reprehenderit dolor beatae ea dolores neque\nfugiat blanditiis voluptate porro vel nihil molestiae ut reiciendis\nqui aperiam non debitis possimus qui neque nisi nulla"}

{

  "body": "test body",

  "id": 101,

  "title": "test title",

  "userId": 101

}

{

  "body": "test body",

  "id": 1,

  "title": "test title",

  "userId": 101

}

{}