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Groovy for Domain-Specific Languages, Second Edition

You're reading from   Groovy for Domain-Specific Languages, Second Edition Extend and enhance your Java applications with domain-specific scripting in Groovy

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Product type Paperback
Published in Sep 2015
Publisher
ISBN-13 9781849695404
Length 386 pages
Edition 1st Edition
Languages
Tools
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Author (1):
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Fergal Dearle Fergal Dearle
Author Profile Icon Fergal Dearle
Fergal Dearle
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Toc

Table of Contents (14) Chapters Close

Preface 1. Introduction to DSLs and Groovy FREE CHAPTER 2. Groovy Quick Start 3. Essential Groovy DSLs 4. The Groovy Language 5. Groovy Closures 6. Example DSL – GeeTwitter 7. Power Groovy DSL Features 8. AST Transformations 9. Existing Groovy DSLs 10. Building a Builder 11. Implementing a Rules DSL 12. Integrating It All Index

Closure parameters


In our previous examples, we have made use of the it keyword. When a closure accepts only a single parameter, we are able to refer to this parameter as it and are free from having to explicitly define the parameter. The possible syntax definitions for a closure are:

  • The default case allows any parameters to be passed to the closure:

    {
    // statements
    }
  • The closure does not accept any parameters:

    { -> 
    // statements
    }
  • The closure can accept one to many parameters with optional type annotations:

    { [type] param (,[type] param)* -> 
    // statements
    }

The parameter list is a comma-separated list of parameter names with optional type definitions. Closures behave slightly different depending on whether we supply the optional type:

given: "Closures with various parameter definition"
    def defaultParams = { println it; }
    def dynamicParams = { something -> println something; }
    def intParams = { int something -> println something; }
    def stringParams = { String something...
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