Configuration

Raft SysMod Configuration

Raft applications are configured using JSON.

Raft supports multiple levels of configuration:

• default-level ... a constant (in Flash memory) JSON document which provides the default (fall-back) configuration for all of the SysMods in the case where there isn't a more specific configuration override.
• sys-type-level ... a JSON document which may completely define the configuration (i.e. entirely override the default-level configuration) or may only override a small part of it or none at all.
• local-mutable-level ... a JSON document which overrides a small part of the configuration and is (generally) localised to a specific SysMod. Configuration of a SysMod involves extraction of the specific part of the overall JSON document - i.e. just the part which relates to that SysMod. So, for instance, if a GPIO pin is to be specified it might be done using the following JSON:

{
  "ExampleSysMod": {
    "ExampleGpioPin": 4,
    "OtherConfigValue": "Example"
  }
}

And the C++ code for the SysMod (which must match the name "ExampleSysMod") which configures the GPIO pin:

int exampleGpioPin = _config.getLong("ExampleGpioPin", -1);

Here the value -1 is a default value which is assigned to exampleGpioPin when a value for the key "ExampleGpioPin" is not present. A test should be done to ensure that a valid GPIO pin value has been assigned before using the value.