Module org.parboiled.core
Package org.parboiled.support

Class Var<T>

java.lang.Object
org.parboiled.common.Reference<T>
org.parboiled.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<T> 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 Var<T> scope (which is automatically initialized with the initial value), so actions in recursive rules work just like expected.

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

  • Constructor Details

    • Var

      public Var()
      Initializes a new Var with a null initial value.

    • Var

      public Var(T value)
      Initializes a new Var with the given initial value.
      Parameters:
      value - the value

    • Var

      public Var(Factory<T> initialValueFactory)
      Initializes a new Var. The given factory will be used to create the initial value for each "execution frame" of the enclosing rule.
      Parameters:
      initialValueFactory - the factory used to create the initial value for a rule execution frame

  • Method Details

    • getName

      public String getName()
      Gets the name of this Var.
      Returns:
      the name

    • setName

      public void setName(String name)
      Sets the name of this Var.
      Parameters:
      name - the name

    • getLevel

      public int getLevel()
      Returns the current frame level of this variable, the very first level corresponding to zero.
      Returns:
      the current level

    • enterFrame

      public boolean enterFrame()
      Provides a new frame for the variable. Potentially existing previous frames are saved. Normally you do not have to call this method manually as parboiled provides for automatic Var frame management.
      Returns:
      true

    • exitFrame

      public boolean exitFrame()
      Exits a frame previously entered with enterFrame(). Normally you do not have to call this method manually as parboiled provides for automatic Var frame management.
      Returns:
      true

    • toString

      public String toString()
      Overrides:
      toString in class Object