ValidationRule

A single validation rule that can be applied to a string value.

Supports the built-in rule types 'required', 'email', 'stringLength', 'pattern', and 'custom', and carries a trigger policy that controls when the rule is evaluated.

Attributes:

Name	Type	Description
`type`	`RuleType`	The validation rule type.
`message`	`str`	Custom error message; if empty a default is generated.
`trigger`	`RuleTriggerType`	When the rule fires — `'always'`, `'blur'`, or `'manual'`.
`params`	`dict`	Additional parameters specific to the rule type (e.g., `min`/`max` for `'stringLength'`, `pattern` for `'pattern'`, `func` for `'custom'`).

init

__init__(rule_type: RuleType, message: str = '', **kwargs)

Create a validation rule.

Parameters:

Name	Type	Description	Default
`rule_type`	`RuleType`	The type of validation to apply.	required
`message`	`str`	Custom error message. If empty, a sensible default is used.	`''`
`**kwargs`		Rule-specific parameters. Pass `trigger` to override the default trigger policy; all other keys are stored in `params` (e.g., `min=3, max=20` for `'stringLength'`, `pattern=r'\d+'` for `'pattern'`, `func=callable` for `'custom'`).	`{}`

validate

validate(value: str) -> ValidationResult

Apply this rule to a value and return the result.

Parameters:

Name	Type	Description	Default
`value`	`str`	The string value to validate.	required

Returns:

Type	Description
`ValidationResult`	A ValidationResult with `is_valid=True` on success or `is_valid=False`
`ValidationResult`	with an error message on failure.