com.github.fge.grappa.support

Class Var<T>

java.lang.Object

com.github.fge.grappa.misc.Reference<T>

com.github.fge.grappa.support.Var<T>

Type Parameters:

T - the type wrapped by this Var

Direct Known Subclasses:

StringBuilderVar, StringVar

public class Var<T>
extends Reference<T>

This class provides a "local variable"-like construct for action expressions in parser rule methods.

Var objects wrap an internal value of an arbitrary (reference) type, can have an initial value, allow read/write access to their values and can be passed around as parameters to nested rule methods.

Each rule invocation (i.e. rule matching attempt) receives its own scope (which is automatically initialized with the initial value), so actions in recursive rules work just like expected.

Var objects generally behave just like local variables with one exception: When rule method rule1() passes a Var defined in its scope to another rule method rule2() as a parameter, and an action in rule method rule2() writes to this Var, all actions in rule method rule1() running after rule2() will "see" this newly written value (since values in Var objects are passed by reference).

Constructor Summary

Constructors

Constructor and Description
Var() Initializes a new Var with a null initial value.
Var(Supplier<T> supplier) Initializes a new Var.
Var(T value) Initializes a new Var with the given initial value.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	enterFrame() Provides a new frame for the variable.
boolean	exitFrame() Exits a frame previously entered with enterFrame().
int	getLevel() Returns the current frame level of this variable, the very first level corresponding to zero.
String	getName() Gets the name of this Var.
void	setName(String name) Sets the name of this Var.
String	toString()

Methods inherited from class com.github.fge.grappa.misc.Reference

clear, get, getAndSet, getNonnull, isSet, set

Methods inherited from class java.lang.Object

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

Constructor Detail

Var

public Var()

Initializes a new Var with a null initial value.

Var

public Var(@Nullable
   T value)

Initializes a new Var with the given initial value.

Parameters:

value - the value

Var

public Var(@Nonnull
   Supplier<T> supplier)

Initializes a new Var. The given supplier will be used to create the initial value for each "execution frame" of the enclosing rule.

Parameters:

supplier - the supplier used to create the initial value for a rule execution frame

Method Detail

getName

public final String getName()

Gets the name of this Var.

Returns:

the name

setName

public final void setName(String name)

Sets the name of this Var.

Parameters:

name - the name

getLevel

public final int getLevel()

Returns the current frame level of this variable, the very first level corresponding to zero.

Returns:

the current level

enterFrame

public final boolean enterFrame()

Provides a new frame for the variable.

Do not use manually!

Returns:

true

exitFrame

public final boolean exitFrame()

Exits a frame previously entered with enterFrame().

Do not use manually!

Returns:

true

toString

public final String toString()

Overrides:

toString in class Object