Question

class User {   
    static constraints = {  
       password(unique:true, length:5..15, validator:{val, obj -> 
          if(val?.equalsIgnoreCase(obj.firstName)) { 
              return false  
          }  
       } 
    } 
}

我发现这种时髦的语法真的令人困惑。我花了几天时间试图学习grails / groovy。我知道它的作用，但我真的不明白。

有人能解释一下这是如何运作的吗？

什么是约束？它是一个闭包，密码被称为函数吗？怎么叫它？

验证器怎么样？

就像我说我能看到它的作用，我只是不明白它是如何做到的。

Answer 1

前言 - 某些部分需要使用Groovy的基本知识。

//Domain Class
class User {
    //A property of the domain class 
    //corresponding to a column in the table User.
    String password

    //Domain classes and Command objects are treated specially in Grails
    //where they have the flexibility of validating the properties 
    //based on the constraints levied on them.
    //Similar functionality can be achieved by a POGO class
    //if it uses @Validateable transformation at the class level.   
    static constraints = {  
       //Constraints is a closure where validation of domain class
       //properties are set which can be validated against when the domain class
       //is saved or validate() is called explicitly.
       //This is driven by AbstractConstraint and Constraint java class 
       //from grails-core

       //Constraint on password field is set below.
       //Here password is not treated as a method call
       //but used to set the parameter name in the constraint class on which
       //validation will be applied against. Refer AbstractConstraint 
       //for the same.
       password(unique:true, size:5..15, validator:{val, obj -> 
          //Each of the key in the above map represents a constraint class 
          //by itself
          //For example: size > SizeConstraint; validator > ValidatorConstraint
          if(val?.equalsIgnoreCase(obj.firstName)) { 
              return false  
          }  
       } 
    } 
}

上面提到了约束如何工作的基础知识。如果您需要了解更多细节，那么如果您对其使用有任何进一步的疑问，请务必访问以下一些来源：

显然，如果您遇到与约束相关的任何实施或更多，那么SO是提问的好地方。随意使用此社区来帮助您克服有问题的程序化情况。

Answer 2

我有同样的问题，也无法找到Groovy书/文档中解释的语法。然后我谷歌找到这个博客：http://www.artima.com/weblogs/viewpost.jsp?thread=291467，它回答了我的问题。

Grails域类语法解释

2 个答案: