groovy.lang
Class Closure

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

All Implemented Interfaces:

GroovyObject, Serializable, Cloneable, Runnable

Direct Known Subclasses:

CurriedClosure, IteratorClosureAdapter, MethodClosure

public abstract class Closure
extends GroovyObjectSupport
implements Cloneable, Runnable, Serializable

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
 

To be able to use a Closure in this way with your own subclass, you need to provide a doCall method with any signature you want to. This ensures that getMaximumNumberOfParameters() and getParameterTypes() will work too without any additional code. If no doCall method is provided a closure must be used in its long form like

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

Version:

$Revision: 19741 $

Author:

James Strachan, John Wilson, Jochen Theodorou, Graeme Rocher

See Also:

Serialized Form

Field Summary

static int	DELEGATE_FIRST With this resolveStrategy set the closure will attempt to resolve property references to the delegate first
static int	DELEGATE_ONLY With this resolveStrategy set the closure will resolve property references to the delegate only and entirely bypass the owner
static int	DONE
protected int	maximumNumberOfParameters
static int	OWNER_FIRST With this resolveStrategy set the closure will attempt to resolve property references to the owner first
static int	OWNER_ONLY With this resolveStrategy set the closure will resolve property references to the owner only and not call the delegate at all
protected Class[]	parameterTypes
static int	SKIP
static int	TO_SELF With this resolveStrategy set the closure will resolve property references to itself and go through the usual MetaClass look-up process.

Constructor Summary

Closure(Object owner)

Closure(Object owner, Object thisObject)

Method Summary

Closure	asWritable()
Object	call() Invokes the closure without any parameters, returning any value if applicable.
Object	call(Object arguments) Invokes the closure, returning any value if applicable.
Object	call(Object[] args)
Object	clone()
Closure	curry(Object[] arguments) Support for Closure currying.
Object	getDelegate()
int	getDirective()
int	getMaximumNumberOfParameters()
Object	getOwner()
Class[]	getParameterTypes()
Object	getProperty(String property) Retrieves a property value.
int	getResolveStrategy() Gets the strategy which the closure users to resolve methods and properties
Object	getThisObject()
boolean	isCase(Object candidate)
Closure	ncurry(int n, Object[] arguments) Support for Closure currying at a given index.
Closure	rcurry(Object[] arguments) Support for Closure "right" currying.
void	run()
void	setDelegate(Object delegate) Allows the delegate to be changed such as when performing markup building
void	setDirective(int directive)
void	setProperty(String property, Object newValue) Sets the given property to the new value.
void	setResolveStrategy(int resolveStrategy) Sets the strategy which the closure uses to resolve property references.
protected static Object	throwRuntimeException(Throwable throwable)

Methods inherited from class groovy.lang.GroovyObjectSupport

getMetaClass, invokeMethod, setMetaClass

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

OWNER_FIRST

public static final int OWNER_FIRST

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

See Also:

Constant Field Values

DELEGATE_FIRST

public static final int DELEGATE_FIRST

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

See Also:

Constant Field Values

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

See Also:

Constant Field Values

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

See Also:

Constant Field Values

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

See Also:

Constant Field Values

DONE

public static final int DONE

See Also:

Constant Field Values

SKIP

public static final int SKIP

See Also:

Constant Field Values

parameterTypes

protected Class[] parameterTypes

maximumNumberOfParameters

protected int maximumNumberOfParameters

Constructor Detail

Closure

public Closure(Object owner,
               Object thisObject)

Closure

public Closure(Object owner)

Method Detail

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:

DELEGATE_FIRST, DELEGATE_ONLY, OWNER_FIRST, OWNER_ONLY, TO_SELF

getResolveStrategy

public int getResolveStrategy()

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

Returns:

The resolve strategy

See Also:

DELEGATE_FIRST, DELEGATE_ONLY, OWNER_FIRST, OWNER_ONLY, TO_SELF

getThisObject

public Object getThisObject()

getProperty

public Object getProperty(String property)

Description copied from interface: GroovyObject

Retrieves a property value.

Specified by:

getProperty in interface GroovyObject

Overrides:

getProperty in class GroovyObjectSupport

Parameters:

property - the name of the property of interest

Returns:

the given property

setProperty

public void setProperty(String property,
                        Object newValue)

Description copied from interface: GroovyObject

Sets the given property to the new value.

Specified by:

setProperty in interface GroovyObject

Overrides:

setProperty in class GroovyObjectSupport

Parameters:

property - the name of the property of interest

newValue - the new value for the property

isCase

public boolean isCase(Object candidate)

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

throwRuntimeException

protected static Object throwRuntimeException(Throwable throwable)

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

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

setDelegate

public void setDelegate(Object delegate)

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

Parameters:

delegate - the new delegate

getParameterTypes

public Class[] getParameterTypes()

Returns:

the parameter types of the longest doCall method of this closure

getMaximumNumberOfParameters

public int getMaximumNumberOfParameters()

Returns:

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

asWritable

public Closure asWritable()

Returns:

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

run

public void run()

Specified by:

run in interface Runnable

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
 

Parameters:

arguments - the arguments to bind

Returns:

the new closure with its arguments bound

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[])

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[])

clone

public Object clone()

Overrides:

clone in class Object

getDirective

public int getDirective()

Returns:

Returns the directive.

setDirective

public void setDirective(int directive)

Parameters:

directive - The directive to set.