Add nlohmann-json example.

examples/example09_nlohmann_json.cpp

@@ -0,0 +1,145 @@
+/*  This file is part of mastodonpp.
+ *  Copyright © 2020 tastytea <tastytea@tastytea.de>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ *  SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ *  OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ *  CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+// Get the last 4 public statuses of an instance and process them with
+// nlohmann-json. <https://github.com/nlohmann/json>
+
+#if __has_include("mastodonpp.hpp")
+#    include "mastodonpp.hpp"            // We're building mastodonpp.
+#else
+#    include <mastodonpp/mastodonpp.hpp> // We're building outside mastodonpp.
+#endif
+
+// Don't compile if nlohmann-json can't be found.
+#if __has_include(<nlohmann/json.hpp>)
+#    include <nlohmann/json.hpp>
+
+#include <cstdlib>
+#include <iostream>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace masto = mastodonpp;
+using json = nlohmann::json;
+using std::exit;
+using std::cout;
+using std::cerr;
+using std::to_string;
+using std::string_view;
+using std::vector;
+
+void handle_error(const masto::answer_type &answer);
+
+int main(int argc, char *argv[])
+{
+    const vector<string_view> args(argv, argv + argc);
+    if (args.size() <= 1)
+    {
+        cerr << "Usage: " << args[0] << " <instance hostname>\n";
+        return 1;
+    }
+
+    try
+    {
+        // Initialize Instance and Connection.
+        masto::Instance instance{args[1], {}};
+        masto::Connection connection{instance};
+
+        // Get the last 4 public statuses of the instance.
+        auto answer{connection.get(masto::API::v1::timelines_public,
+                                   {
+                                       {"limit", "4"},
+                                       {"local", "true"}
+                                   })};
+        if (answer)
+        {
+            // Parse JSON string.
+            auto statuses{json::parse(answer.body)};
+            for (const auto &status : statuses)
+            {
+                // Extract the info we want and print it.
+                const auto acct{status["account"]["acct"].get<string_view>()};
+                const auto content{status["content"].get<string_view>()};
+                const auto id{status["id"].get<string_view>()};
+                cout << acct << " wrote status " << id << ": \n";
+                cout << "  " << content.substr(0, 76) << " …\n";
+
+                // Print tags if there are any.
+                const auto tags{status["tags"]};
+                if (!tags.empty())
+                {
+                    cout << "    Tags: ";
+                    for (const auto &tag : tags)
+                    {
+                        cout << '#' << tag["name"].get<string_view>() << " ";
+                    }
+                    cout << '\n';
+                }
+
+                // Print the number of attachments.
+                const auto n_attachments{status["media_attachments"].size()};
+                if (n_attachments > 0)
+                {
+                    cout << "    " << n_attachments << " attachment";
+                    if (n_attachments > 1)
+                    {
+                        cout << "s";
+                    }
+                    cout << ".\n";
+                }
+            }
+        }
+        else
+        {
+            handle_error(answer);
+        }
+
+    }
+    catch (const masto::CURLException &e)
+    {
+        // Only libcurl errors that are not network errors will be thrown.
+        // There went probably something wrong with the initialization.
+        cerr << e.what() << '\n';
+    }
+}
+
+void handle_error(const masto::answer_type &answer)
+{
+    if (answer.curl_error_code == 0)
+    {
+        // If it is no libcurl error, it must be an HTTP error.
+        cerr << "HTTP status: " << answer.http_status << '\n';
+    }
+    else
+    {
+        // Network errors like “Couldn't resolve host.”.
+        cerr << "libcurl error " << to_string(answer.curl_error_code)
+             << ": " << answer.error_message << '\n';
+    }
+
+    exit(1);
+}
+
+#else
+
+#include <iostream>
+int main()
+{
+    std::cout << "Example could not be compiled "
+        "because nlohmann-json was not found.\n";
+}
+
+#endif  // __has_include(<nlohmann/json.hpp>)

include/mastodonpp.hpp

@@ -106,6 +106,7 @@
  *  @example example06_update_name.cpp
  *  @example example07_delete_status.cpp
  *  @example example08_obtain_token.cpp
+ *  @example example09_nlohmann_json.cpp
  */
 
 /*!