groovy.lang
[Java] Class Closure

java.lang.Object
  groovy.lang.GroovyObjectSupport
      groovy.lang.Closure

All Implemented Interfaces:

Cloneable, Runnable, Serializable

public abstract class Closure
extends GroovyObjectSupport

Represents any closure object in Groovy.

Groovy allows instances of Closures to be called in a short form. For example:

   def a = 1
   def c = {a}
   assert c() == 1
 

   def a = 1
   def c = {a}
   assert c.call() == 1
 

Authors:

James Strachan

John Wilson

Jochen Theodorou

Graeme Rocher

Version:

\$Revision: 21242 \$

DELEGATE_FIRST

public static final int DELEGATE_FIRST

With this resolveStrategy set the closure will attempt to resolve property references to the delegate first

DELEGATE_ONLY

public static final int DELEGATE_ONLY

With this resolveStrategy set the closure will resolve property references to the delegate only and entirely bypass the owner

DONE

public static final int DONE

OWNER_FIRST

public static final int OWNER_FIRST

With this resolveStrategy set the closure will attempt to resolve property references to the owner first

OWNER_ONLY

public static final int OWNER_ONLY

With this resolveStrategy set the closure will resolve property references to the owner only and not call the delegate at all

SKIP

public static final int SKIP

TO_SELF

public static final int TO_SELF

With this resolveStrategy set the closure will resolve property references to itself and go through the usual MetaClass look-up process. This allows the developer to override getProperty using ExpandoMetaClass of the closure itself

maximumNumberOfParameters

protected int maximumNumberOfParameters

parameterTypes

protected Class[] parameterTypes

Closure

public Closure(Object owner, Object thisObject)

Closure

public Closure(Object owner)

Constructor used when the "this" object for the Closure is null. This is rarely the case in normal Groovy usage.

Parameters:

owner - the Closure owner

asWritable

public Closure asWritable()

Returns:

a version of this closure which implements Writable. Note that the returned Writable also overrides toString() in order to allow rendering the result directly to a String.

call

public Object call()

Invokes the closure without any parameters, returning any value if applicable.

Returns:

the value if applicable or null if there is no return statement in the closure

call

public Object call(Object[] args)

call

public Object call(Object arguments)

Invokes the closure, returning any value if applicable.

Parameters:

arguments - could be a single value or a List of values

Returns:

the value if applicable or null if there is no return statement in the closure

clone

public Object clone()

curry

public Closure curry(Object[] arguments)

Support for Closure currying.

Typical usage:

 def multiply = { a, b -> a * b }
 def doubler = multiply.curry(2)
 assert doubler(4) == 8
 

Note: special treatment is given to Closure vararg-style capability. If you curry a vararg parameter, you don't consume the entire vararg array but instead the first parameter of the vararg array as the following example shows:

 def a = { one, two, Object[] others -> one + two + others.sum() }
 assert a.parameterTypes.name == ['java.lang.Object', 'java.lang.Object', '[Ljava.lang.Object;']
 assert a(1,2,3,4) == 10
 def b = a.curry(1)
 assert b.parameterTypes.name == ['java.lang.Object', '[Ljava.lang.Object;']
 assert b(2,3,4) == 10
 def c = b.curry(2)
 assert c.parameterTypes.name == ['[Ljava.lang.Object;']
 assert c(3,4) == 10
 def d = c.curry(3)
 assert d.parameterTypes.name == ['[Ljava.lang.Object;']
 assert d(4) == 10
 def e = d.curry(4)
 assert e.parameterTypes.name == ['[Ljava.lang.Object;']
 assert e() == 10
 assert e(5) == 15
 

Parameters:

arguments - the arguments to bind

Returns:

the new closure with its arguments bound

getDelegate

public Object getDelegate()

Returns:

the delegate Object to which method calls will go which is typically the outer class when the closure is constructed

getDirective

public int getDirective()

Returns:

Returns the directive.

getMaximumNumberOfParameters

public int getMaximumNumberOfParameters()

Returns:

the maximum number of parameters a doCall method of this closure can take

getOwner

public Object getOwner()

Returns:

the owner Object to which method calls will go which is typically the outer class when the closure is constructed

getParameterTypes

public Class[] getParameterTypes()

Returns:

the parameter types of the longest doCall method of this closure

getProperty

public Object getProperty(String property)

getResolveStrategy

public int getResolveStrategy()

Gets the strategy which the closure users to resolve methods and properties

Returns:

The resolve strategy

See Also:

Closure.DELEGATE_FIRST

Closure.DELEGATE_ONLY

Closure.OWNER_FIRST

Closure.OWNER_ONLY

Closure.TO_SELF

getThisObject

public Object getThisObject()

isCase

public boolean isCase(Object candidate)

ncurry

public Closure ncurry(int n, Object[] arguments)

Support for Closure currying at a given index. Parameters are supplied from index position "n". Typical usage:

 def caseInsensitive = { a, b -> a.toLowerCase() <=> b.toLowerCase() } as Comparator
 def caseSensitive = { a, b -> a <=> b } as Comparator
 def animals1 = ['ant', 'dog', 'BEE']
 def animals2 = animals1 + ['Cat']
 // curry middle param of this utility method:
 // Collections#binarySearch(List list, Object key, Comparator c)
 def catSearcher = Collections.&binarySearch.ncurry(1, "cat")
 [[animals1, animals2], [caseInsensitive, caseSensitive]].combinations().each{ a, c ->
   def idx = catSearcher(a.sort(c), c)
   print a.sort(c).toString().padRight(22)
   if (idx < 0) println "Not found but would belong in position ${-idx - 1}"
   else println "Found at index $idx"
 }
 // =>
 // [ant, BEE, dog]       Not found but would belong in position 2
 // [ant, BEE, Cat, dog]  Found at index 2
 // [BEE, ant, dog]       Not found but would belong in position 2
 // [BEE, Cat, ant, dog]  Not found but would belong in position 3
 

Parameters:

n - the index from which to bind parameters (may be -ve in which case it will be normalized)

arguments - the arguments to bind

Returns:

the new closure with its arguments bound

See Also:

curry(Object[])

rcurry

public Closure rcurry(Object[] arguments)

Support for Closure "right" currying. Parameters are supplied on the right rather than left as per the normal curry() method. Typical usage:

 def divide = { a, b -> a / b }
 def halver = divide.rcurry(2)
 assert halver(8) == 4
 

Parameters:

arguments - the arguments to bind

Returns:

the new closure with its arguments bound

See Also:

curry(Object[])

run

public void run()

setDelegate

public void setDelegate(Object delegate)

Allows the delegate to be changed such as when performing markup building

Parameters:

delegate - the new delegate

setDirective

public void setDirective(int directive)

Parameters:

directive - The directive to set.

setProperty

public void setProperty(String property, Object newValue)

setResolveStrategy

public void setResolveStrategy(int resolveStrategy)

Sets the strategy which the closure uses to resolve property references. The default is Closure.OWNER_FIRST

Parameters:

resolveStrategy - The resolve strategy to set

See Also:

Closure.DELEGATE_FIRST

Closure.DELEGATE_ONLY

Closure.OWNER_FIRST

Closure.OWNER_ONLY

Closure.TO_SELF

throwRuntimeException

protected static Object throwRuntimeException(Throwable throwable)

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