migrations.py 文件源码

def alter_field(old_field, new_field, filters: List[str]):
    """Alters a field from one state to the other.

    Arguments:
        old_field:
            The field before altering it.

        new_field:
            The field after altering it.

        filters:
            List of strings to filter
            SQL statements on.
    """

    model = define_fake_model({'title': old_field})
    project = migrations.state.ProjectState.from_apps(apps)

    with connection.schema_editor() as schema_editor:
        execute_migration(schema_editor, [
            migrations.CreateModel(
                model.__name__,
                fields=[
                    ('title', old_field.clone())
                ]
            )
        ], project)

    with filtered_schema_editor(*filters) as (schema_editor, calls):
        execute_migration(schema_editor, [
            migrations.AlterField(
                model.__name__,
                'title',
                new_field
            )
        ], project)

    yield calls