Writing custom type converter¶
Type conversions are described in yaml config files. CppBind supports several primitive and complex types and has default implementation of the type converters for those types: int, char, bool, enum, std::string, std::vector, user-defined classes/structs, etc. The implementation details about these converters for supported languages can be found here.
Besides of supported types, CppBind also allows writing custom type converters for your types. The config files must be placed under the directory defined by custom_config_dir variable. CppBind includes all files with *_types.yaml name pattern in project default config file. So either your files must have _types.yaml suffix or you need to include your custom type converter config files under rules section in your project config file:
rules:
swift.type_converters:
!include your_snippets_dir/your_custom_snippet_file.yaml
Since CppBind finds and merges rules which are spread all over the project, you can also have a separate file where rules section can be defined and then merged with other rules sections in project config files. More information about merging mechanism can be found Section rules.
To write a custom type converter you need to fill the type converter required sections with correct snippets. The required fields are type information sections and conversion sections from source to target languages. More information about type converter sections can be found here.
The following is an example of nlohmann::json converter:
nlohmann::json:
custom:
is_c_pointer_type: True
tname: JSON
types:
swift: String
c: char *
sc: UnsafeMutablePointer<CChar>
converters:
c_to_cxx: |
auto {{target_name}} = nlohmann::json::parse({{name}});
free({{name}});
cxx_to_c: |
auto {{name}}_str = {{name}}.dump();
auto {{target_name}} = strdup({{name}}_str.c_str());
swift_to_sc: |
let {{target_name}} = strdup({{name}})!
sc_to_swift: |
let {{target_name}} = String(cString: {{name}})
defer {
{{name}}.deallocate()
}
nlohmann::json:
custom:
pname: Object
tname: JSON
types:
kotlin: String
jni: jstring
jdk: String
converters:
jni_to_cxx: |
auto {{target_name}} = nlohmann::json::parse(cppbind::jni_to_string(env, {{name}}));
cxx_to_jni: |
{{target_type_name}} {{target_name}} = cppbind::string_to_jni(env, {{name}}.dump(4));
kotlin_to_jdk:
jdk_to_kotlin: