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(Quick Reference) # constraints ## Purpose Allows the definition of declarative validation constraints. See Validation in the user guide. ## Examples

    class Book {    String title
        Author author    static constraints = {
            title blank: false, size: 5..150
            author nullable: true
        }
    }
## Description Constraints are defined using the declarative constraints DSL as described in the Validation section of the user guide. Once evaluated, validation can be applied through the use of the validate method:
    def b = new Book()
    assert !b.validate()
A list of ConstrainedProperty instances applied against the domain class by the `constraints` property is available at runtime:
    for (constraint in b.constraints) {
        println it.name
        println it.maxSize
    }
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