Null

Null is one shared object that means “there is nothing here” (NSNull in shape). A collection stores Object*, and a null reference usually means absent. Sometimes a slot needs an explicit nothing that is still an object: a sparse row, a JSON null, a cleared entry that must keep its place.

#import "Null.xc"          // or the Foundation umbrella

Overview

Array* row = new Array();
row.add(Null.null());                   // a gap that keeps its index
if (Null.isNothing(row.get(0)))    // a null reference or Null.null()
    …

There is only ever one instance, so compare with isNull or by reference. Its description is null. JSON reads null as this object.

Topics

· null · isNull · isNothing · description

null

static Null* null(void)

The shared instance.

isNull

static bool isNull(Object* o)

Whether o is the shared instance. A null reference is not.

isNothing

static bool isNothing(Object* o)

Whether o is a null reference or the shared instance.

description

String* description(void)

null.

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