Add an example for how to use with cmake-submodules

fix #147
fix #148

README.md

@@ -121,6 +121,8 @@ access nlohmann-json:
 a sub-directory (via `add_subdirectory()`), 2 and 3 can be
 assisted by setting the `nlohmann_json_DIR`-variable.
 
+For 1 there is an example of you to do in example/cmake-submodule.
+
 ### Building with Hunter package manager
 
 To enable access to nlohmann json library, Hunter can be used. Just run with HUNTER_ENABLED=ON option. No further dependencies needed

example/cmake-submodule/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.2)
+
+project(simple-json-validator-as-submodule-test)
+
+# absolute-path
+set(PATH_TO_NLOHMANN_JSON_REPO $ENV{HOME}/devel/upstream/json)
+
+# build shared library
+set(BUILD_SHARED_LIBS ON)
+
+# JSON library
+option(JSON_BuildTests OFF)
+add_subdirectory(${PATH_TO_NLOHMANN_JSON_REPO}
+                 json-binary-dir
+                 EXCLUDE_FROM_ALL)
+
+# JSON SCHEMA VALIDATOR library
+option(BUILD_TESTS OFF)
+add_subdirectory(../..
+                 json-validator-binary-dir
+                 EXCLUDE_FROM_ALL)
+
+add_executable(validate validate.cpp)
+target_link_libraries(validate nlohmann_json_schema_validator)

example/cmake-submodule/validate.cpp

@@ -0,0 +1,20 @@
+#include <nlohmann/json-schema.hpp>
+
+#include <iostream>
+
+int main(void)
+{
+	nlohmann::json schema_json{{"type", "number"}};
+	nlohmann::json_schema::json_validator validator;
+
+	validator.set_root_schema(schema_json);
+
+	validator.validate(1);
+	try {
+		validator.validate("\"1\"");
+	} catch (const std::exception &e) {
+		std::cerr << "expected exception: " << e.what() << "\n";
+		return EXIT_SUCCESS;
+	}
+	return EXIT_FAILURE;
+}