如何重载一些Groovy类型转换以避免NumberFormatException的try / catch？ [英] How to overload some Groovy Type conversion for avoiding try/catch of NumberFormatException?

问题描述

我厌倦了用 try / catch 块封装每个 asType 的调用。

  def b =
 def c 
尝试{
c = b as整数
} 
 catch（NumberFormatException）{
c = null 
} 
 println c 
  

而是我想在我的代码中写入以下内容：

  def b =
 def c = b as Integer 
  

如果 b 格式不正确，那么我希望将 null 分配给 c

那我该如何重载 asType 运算符的默认行为？

是吗？如果我为我的整个Grails应用程序执行操作会有风险吗？或者是简单地创建我自己的方法（如 asTypeSafe ）并称之为最佳解决方案？ Groovy / Grails是否对Groovy类型转换进行了一些配置调整？

编辑（对于实施答案感兴趣的人）
根据接受的答案，我将以下代码添加到我的bootstrap.groovy文件，它完美的工作。

  String.metaClass.asTypeSafe = {Class c  - > 
 try {
 delegate.asType（c）
} 
 catch（Exception）{
 return null 
} 
} 
  

我把它称为如下：

  def myNum = myStr.asTypeSafe（Integer）
  

解决方案

您可以通过提供新的asType实现来覆盖默认行为。确保你保存旧的，并为其他你不想处理的课程打电话。例子：

  oldAsType = String.metaClass.getMetaMethod（asType，[Class] as Class []）
 String.metaClass.asType = {Class c  - > 
 if（c == Integer）{
 delegate.isInteger（）？ delegate.toInteger（）：null 
} else {
 oldAsType.invoke（delegate，c）
} 
} 
  

至于这是否是一个好主意，请记住很多对象将使用字符串，而且很有可能他们称这种转换为依赖于异常抛出。如果你从一个params对象中传入一个params对象，那么Grails域对象将完成大量的类型转换工作。控制器，但我认为它对这种事情没有任何形式的全局调整。

I am sick of encapsuling each call of asType with try/catch block like :

def b = ""
def c 
try {
    c = b as Integer
}
catch (NumberFormatException) {
    c = null
}
println c

instead I would like to write in my code the following:

def b = ""
def c = b as Integer

and if b is not well-formatted, then I want to have null be assigned to c

So how can I overload this default behavior for the asType operator ?

Is it risky if I do it for my entire Grails application? Or is the best solution to simply create a method of my own (like asTypeSafe) and call it ? Do Groovy/Grails have some configuration tweaks regarding Groovy Type conversion?

EDIT (for people interested in the implemented answer) Based on the accepted answer, I have added the following code to my bootstrap.groovy file and it works perfectly.

String.metaClass.asTypeSafe = {Class c ->
    try {
        delegate.asType(c)
    }
    catch (Exception) {
        return null
    }
}

and I call it as below:

def myNum = myStr.asTypeSafe(Integer)

解决方案

You can override the default behavior by providing a new asType implementation. Make sure you save the old one, and call it for other classes you don't want to handle yourself. Example:

oldAsType = String.metaClass.getMetaMethod("asType", [Class] as Class[])
String.metaClass.asType = { Class c ->
    if (c == Integer) { 
        delegate.isInteger() ? delegate.toInteger() : null
    } else {
        oldAsType.invoke(delegate, c)
    }
} 

As for whether this is a good idea, just remember that a lot of objects will be be using Strings and it's quite possible they call this conversion and rely on the exception being thrown. You're messing with things at quite a low level.

Grails domain objects will do a lot of the heavy lifting of type conversion if you pass in a params object from a controller, but I don't think it has any kind of global tweaks for this kind of thing.

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