Step models

The steps of the solution are typically associated with the pages of the solution app UI. A step is defined in a step definition file, which must include at least one field and can include one or more methods.

When you create a solution by invoking the ansys-templates tool’s new solution command, two step definition template files are created in the <solution name>/src/ansys/solutions/<solution name>/solution directory:

• first_step.py

• other_step.py

Note

For the sake of clarity, this documentation assumes that steps are defined individually, each in a separate module. However, you can adjust the structure of your solution definition as needed. For example, the steps for a simple solution could all be defined in a single file.

Define a step

Define a solution step as a class with inheritance from the StepModel base class (imported from ansys.saf.glow.solution). For example, the template files first_step.py and other_step.py define the step classes FirstStep and OtherStep, respectively.

At minimum, each step must have at least one field. Each field must have a name, type, and default value defined using the following syntax: name: type = value

Note

Internally, step fields are defined using Pydantic, so you can use all the field types available from Pydantic and use Pydantic practices to implement your own types.

For the minimal sample solution, the step definition in shown below defines the step class MinimalStep. This class has a single field named x, with type int and a default value of 99.

minimal\solution\minimal_step.py

from ansys.saf.glow.solution import StepModel


class MinimalStep01(StepModel):
    x: int = 99

If a field has no default value, then you must designate it as Optional. For example, in the step class NoDefaultStep, the optional_thing field has a type of str and no default value.

minimal\solution\no_default_step.py

from ansys.saf.glow.solution import StepModel


class NoDefaultStep(StepModel):
    x: int = 99
    name: str = "Field Name"
    optional_thing: Optional[str]

If you want to declare a custom field type, it can be done by inheriting from Pydantic’s BaseModel.

minimal\solution\custom_type.py

from ansys.saf.glow.solution import StepModel
from pydantic import BaseModel


class CustomType(BaseModel):
    x: int
    y: int
    z: int


class CustomTypeStep(StepModel):
    custom_type: CustomType = CustomType(x=1, y=2, z=3)

Additional examples are available in Pydantic’s Models documentation.

In development mode, the type of a field may change. Every project created before the change cannot be run again, as Pydantic will find a conflict. More generally, every time a change is brought to a step class, Ansys recommends that you start with a fresh project.

Add steps to a solution

Add steps to a solution using a Steps class with inheritance from the StepsModel base class (imported from ansys.saf.glow.solution).

At minimum, the Steps class must have at least one field. Each field maps the name of a given step to the type of that step (the step class) using the following syntax: name: type

Add a field for each of the steps defined for the solution.

The Steps class shown below includes fields for the two template steps provided.

minimal\solution\definition.py

class Steps(StepsModel):
    first_step: FirstStep
    other_step: OtherStep

Note that the step name must be unique, but the type can be reused. For example, in the code sample below, there are two steps with type FirstStep.

minimal\solution\definition.py

class Steps(StepsModel):
    first_step: FirstStep
    other_step: OtherStep
    miniimal_step: MinimalStep
    no_default_step: NoDefaultStep
    duplicate_type_step: FirstStep
    last_step: LastStep