org.erights.e.elib.slot
Class NullOkGuard

java.lang.Object
  |
  +--org.erights.e.elib.slot.BaseGuard
        |
        +--org.erights.e.elib.slot.NullOkGuard

All Implemented Interfaces:

Guard, SlotGuard, ValueGuard

public class NullOkGuard

extends BaseGuard

Safe: The canonical instance (THE_ONE) is bound to "nullOk" in the initial environment, and accepts null as a valid value.

As a ValueGuard, "nullOk" accepts only null as a valid value.

As a SlotGuard, "nullOk" makes a settable slot that only accepts nulls.

As a ValueGuard & SlotGuard template, "nullOk(valueGuard)" produces an object that implements ValueGuard and SlotGuard. (This object is also an instance of NullOkGuard, but no one should care.) As a ValueGuard, this object accepts null and whatever the argument valueGuard accepts. As a SlotGuard, it makes settable slots that accept null and whatever the original valueGuard accepts. In both cases, non-null values are coerced according to the original valueGuard.

Author:

Mark S. Miller

Field Summary

private ValueGuard	myOptSubGuard
static NullOkGuard	THE_ONE Enabled:

Fields inherited from class org.erights.e.elib.slot.BaseGuard

myOptValueGuard

Constructor Summary

private

NullOkGuard(ValueGuard optSubGuard)

Method Summary

Object	coerce(Object specimen, OneArgFunc optEjector) Enabled: If specimen is null, returns null.
String	getName() Enabled: "nullOk" or "nullOk(sub-guard-name)"
NullOkGuard	run(ValueGuard subGuard) Enabled: Makes a Guard that accepts either null or values that the argument 'subGuard' accepts.

Methods inherited from class org.erights.e.elib.slot.BaseGuard

__printOn, accepts, and, butNot, coerce, get, makeSlot, makeSlot, not, or, toString, xor

Methods inherited from class java.lang.Object

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

Field Detail

THE_ONE

public static final NullOkGuard THE_ONE

Enabled:

myOptSubGuard

private final ValueGuard myOptSubGuard

Constructor Detail

NullOkGuard

private NullOkGuard(ValueGuard optSubGuard)

Method Detail

coerce

public Object coerce(Object specimen,
                     OneArgFunc optEjector)

Enabled: If specimen is null, returns null. Otherwise passes it to my wrapped ValueGuard, if there is one.

Specified by:

coerce in interface ValueGuard

Overrides:

coerce in class BaseGuard

run

public NullOkGuard run(ValueGuard subGuard)

Enabled: Makes a Guard that accepts either null or values that the argument 'subGuard' accepts.

Non-null values are coerced by the argument. As a SlotGuard, makes settable slots.

getName

public String getName()

Enabled: "nullOk" or "nullOk(sub-guard-name)"

Specified by:

getName in interface SlotGuard

Overrides:

getName in class BaseGuard