Add some example code that was prepared for a Melbourne C++ lightning…

… talk

CMakeLists.txt

@@ -80,6 +80,26 @@ add_executable(external_schema
     examples/external_schema.cpp
 )
 
+add_executable(array_iteration_basics
+    examples/array_iteration_basics.cpp
+)
+
+add_executable(array_iteration_template_fn
+    examples/array_iteration_template_fn.cpp
+)
+
+add_executable(object_iteration
+    examples/object_iteration.cpp
+)
+
+add_executable(json_pointers
+    examples/json_pointers.cpp
+)
+
+add_executable(remote_resolution
+    examples/remote_resolution.cpp
+)
+
 set(TEST_SOURCES
     tests/test_adapter_comparison.cpp
     tests/test_fetch_document_callback.cpp
@@ -121,3 +141,8 @@ endif()
 target_link_libraries(test_suite ${TEST_LIBS} ${Boost_LIBRARIES})
 target_link_libraries(custom_schema ${Boost_LIBRARIES})
 target_link_libraries(external_schema ${Boost_LIBRARIES})
+target_link_libraries(array_iteration_basics jsoncpp)
+target_link_libraries(array_iteration_template_fn jsoncpp)
+target_link_libraries(object_iteration jsoncpp)
+target_link_libraries(json_pointers)
+target_link_libraries(remote_resolution curl curlpp)

examples/array_iteration_basics.cpp

@@ -0,0 +1,132 @@
+/**
+ * @file
+ *
+ * @brief Demonstrates iteration over an array and type check functions
+ *
+ */
+
+#include <exception>
+#include <iostream>
+
+// jsoncpp
+#include <json/json.h>
+#include <valijson/adapters/jsoncpp_adapter.hpp>
+#include <valijson/utils/jsoncpp_utils.hpp>
+
+// RapidJSON
+#include <rapidjson/document.h>
+#include <valijson/adapters/rapidjson_adapter.hpp>
+#include <valijson/utils/rapidjson_utils.hpp>
+
+using std::cerr;
+using std::cout;
+using std::endl;
+using std::runtime_error;
+
+// The first example uses RapidJson to load a JSON document. If the document
+// contains an array, this function will print any array values that have a
+// valid string representation.
+void usingRapidJson(const char *filename);
+
+// The second example uses JsonCpp to perform the same task, but unlike the
+// RapidJson example, we see how to use strict type checks and exception
+// handling.
+void usingJsonCpp(const char *filename);
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        cerr << "Usage: " << endl;
+        cerr << "  " << argv[0] << " <filename>" << endl;
+        return 1;
+    }
+
+    // Load the document using rapidjson
+    cout << "-- Iteration using RapidJSON --" << endl;
+    usingRapidJson(argv[1]);
+    cout << endl;
+
+    // Load the document using jsoncpp
+    cout << "-- Iteration using jsoncpp --" << endl;
+    usingJsonCpp(argv[1]);
+    cout << endl;
+
+    return 0;
+}
+
+void usingRapidJson(const char *filename)
+{
+    using valijson::adapters::RapidJsonAdapter;
+
+    rapidjson::Document document;
+    if (!valijson::utils::loadDocument(filename, document)) {
+        return;
+    }
+
+    RapidJsonAdapter adapter(document);
+    if (!adapter.isArray()) {
+        cout << "Not an array." << endl;
+        return;
+    }
+
+    cout << "Array values:" << endl;
+    int index = 0;
+
+    // We support the old way of doing things...
+    const RapidJsonAdapter::Array array = adapter.asArray();
+    for (RapidJsonAdapter::Array::const_iterator itr = array.begin(); 
+                                                 itr != array.end(); ++itr) {
+        cout << "  " << index++ << ": ";
+
+        // Each element of the array is just another RapidJsonAdapter
+        const RapidJsonAdapter &value = *itr;
+
+        // maybeString is a loose type check
+        if (value.maybeString()) {
+            // If a value may be a string, we are allowed to get a string 
+            // representation of the value using asString
+            cout << value.asString();
+        }
+
+        cout << endl;
+    }
+}
+
+void usingJsonCpp(const char *filename)
+{
+    Json::Value value;
+    if (!valijson::utils::loadDocument(filename, value)) {
+        return;
+    }
+
+    valijson::adapters::JsonCppAdapter adapter(value);
+
+    // isArray is a strict type check
+    if (!adapter.isArray()) {
+        cout << "Not an array." << endl;
+        return;
+    }
+
+    cout << "Array values:" << endl;
+    int index = 0;
+
+    // If a value is not an array, then calling getArray will cause a runtime
+    // exception to be raised.
+    for (auto value : adapter.getArray()) {
+        cout << "  " << index++ << ": ";
+
+        // isString is another strict type check. Valijson uses the convention
+        // that strict type check functions are prefixed with 'is'.
+        if (!value.isString()) {
+            cout << "Not a string. ";
+        }
+
+        try {
+            // Also by convention, functions prefixed with 'get' will raise a
+            // runtime exception if the value is not of the correct type.
+            cout << value.getString() << endl;
+        } catch (runtime_error &e) {
+            cout << "Caught exception: " << e.what() << endl;
+        }
+    }
+}

examples/array_iteration_template_fn.cpp

@@ -0,0 +1,65 @@
+/**
+ * @file
+ *
+ * @brief Demonstrates iteration over an array using template functions
+ *
+ */
+
+#include <iostream>
+
+#include <json/json.h>
+#include <valijson/adapters/jsoncpp_adapter.hpp>
+#include <valijson/utils/jsoncpp_utils.hpp>
+
+using std::cerr;
+using std::cout;
+using std::endl;
+
+template<class AdapterType>
+void iterateJsonArray(const AdapterType &adapter)
+{
+    if (!adapter.isArray()) {
+        cout << "Not an array." << endl;
+        return;
+    }
+
+    cout << "Array values:" << endl;
+    int index = 0;
+
+    for (auto value : adapter.getArray()) {
+        cout << "  " << index++ << ": ";
+
+        if (value.maybeString()) {
+            cout << value.asString();
+        }
+
+        cout << endl;
+    }
+}
+
+void usingJsonCppWithTemplateFn(const char *filename)
+{
+    Json::Value value;
+    if (!valijson::utils::loadDocument(filename, value)) {
+        return;
+    }
+
+    valijson::adapters::JsonCppAdapter adapter(value);
+    iterateJsonArray(adapter);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        cerr << "Usage: " << endl;
+        cerr << "  " << argv[0] << " <filename>" << endl;
+        return 1;
+    }
+
+    // Load the document using jsoncpp and iterate over array using function template
+    cout << "-- Array iteration using jsoncpp via template function --" << endl;
+    usingJsonCppWithTemplateFn(argv[1]);
+    cout << endl;
+
+    return 0;
+}

examples/json_pointers.cpp

@@ -0,0 +1,110 @@
+/**
+ * @file
+ *
+ * @brief Demonstrates how to resolve JSON pointers against the current document
+ *
+ */
+
+#include <iostream>
+
+#include <rapidjson/document.h>
+
+#include <valijson/adapters/rapidjson_adapter.hpp>
+#include <valijson/internal/json_pointer.hpp>
+#include <valijson/internal/json_reference.hpp>
+#include <valijson/utils/rapidjson_utils.hpp>
+
+using std::cerr;
+using std::cout;
+using std::endl;
+
+template<typename AdapterType>
+std::string maybeResolveRef(const AdapterType &value, const AdapterType &root)
+{
+    if (!value.isObject()) {
+        // Not an object, therefore not a JSON reference
+        return "";
+    }
+
+    const auto &object = value.getObject();
+    const auto itr = object.find("$ref");
+    if (itr == object.end()) {
+        // Object does not contain $ref property
+        return "";
+    }
+
+    const AdapterType maybeRef = itr->second;
+    if (!maybeRef.isString()) {
+        return "[$ref did not contain a string value]";
+    }
+
+    // Attempt to extract a JSON pointer
+    const std::string ref = maybeRef.getString();
+    const auto maybePointer = valijson::internal::json_reference::getJsonReferencePointer(ref);
+    if (!maybePointer) {
+        return "[$ref did not contain valid JSON pointer]";
+    }
+
+    const auto refAdapter = valijson::internal::json_pointer::resolveJsonPointer(root, *maybePointer);
+    if (!refAdapter.maybeString()) {
+        return "[$ref did not point to a string value]";
+    }
+
+    return refAdapter.asString();
+}
+
+template<typename AdapterType>
+void iterateJsonObject(const AdapterType &adapter)
+{
+    if (!adapter.maybeObject()) {
+        cout << "Not an object." << endl;
+        return;
+    }
+
+    cout << "Object members:" << endl;
+
+    // JSON objects are an unordered collection of key-value pairs,
+    // so the members of the object may be printed in an order that is
+    // different to that in the source JSON document.
+    for (auto member : adapter.asObject()) {
+        // The key is a std::string that can be accessed using 'first'
+        cout << "  " << member.first << ": ";
+
+        // The value is just another Adapter, and can be accessed using 'second'
+        const AdapterType &value = member.second;
+        if (value.maybeString()) {
+            cout << value.asString();
+        } else {
+            cout << maybeResolveRef(value, adapter);
+        }
+
+        cout << endl;
+    }
+}
+
+void usingJsonCppWithTemplateFn(const char *filename)
+{
+    rapidjson::Document document;
+    if (!valijson::utils::loadDocument(filename, document)) {
+        return;
+    }
+
+    valijson::adapters::RapidJsonAdapter adapter(document);
+    iterateJsonObject(adapter);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        cerr << "Usage: " << endl;
+        cerr << "  " << argv[0] << " <filename>" << endl;
+        return 1;
+    }
+
+    // Load the document using jsoncpp and iterate over array using function template
+    cout << "-- Resolving JSON pointers using RapidJSON --" << endl;
+    usingJsonCppWithTemplateFn(argv[1]);
+    cout << endl;
+
+    return 0;
+}