Model components

Note

This page is only about how to use components, not how to create a custom one. if you want to create a custom component or add default components to your custom model please refer to Custom components or Custom Models

Model components are how HydroMT specifies a lot of it’s behaviors. The plugins can make specialized components that can then be used to achieve basically anything you want that is within the scope of hydromt.

The anatomy of a components

Components in hydromt receive a reference back to the model they are a part of, so that they can access more global properties of the model such as the root, the data catalog and the write permissions as well as other components. This means that components can’t effectively exit outside of a model.

There are basically two ways to add a component to a model: using the workflow yaml and using the python interface. For more detail on how components are created and accessed from the workflow file see this page

Adding components using the Python interface

Below is an example of how to construct a component (in this case a ConfigComponent) and how to add it to the model. Below we’ll give a more detailed explanation of the steps.

from hydromt.model.component import ConfigComponent
from hydromt.model import Model

model = Model(mode="w", root=str("tmp"))

config_component = ConfigComponent(model)
model.add_component("config", config_component)
model.config.set("test.data", "value")

As previously mentioned when creating a component, a model needs to be constructed first so that the component can gain a reference to it, so this is the first step.

Secondly the component is created with the model being passed as an argument (the reference will be created for you by the component itself).

Note that while the component now has access to the model, the model does not yet have access to the component because it has not been told about it. This is done by the add_component step. Here it takes a name (must be a valid python name) and a component as an argument.

After a component has been added to a model. it can be accessed as a property on the model (this is why it must be a valid python name)