Symbol constructor Null safety
- String name
Constructs a new Symbol representing the provided name.
The name must be a valid public Dart member name, public constructor name, or library name, optionally qualified.
A qualified name is a valid name preceded by a public identifier name
and a '
foo.bar.baz= is a qualified version of
That means that the content of the
name String must be either
- a valid public Dart identifier
(that is, an identifier not starting with "
- such an identifier followed by "=" (a setter name),
- the name of a declarable operator
(one of "
=", or "
- any of the above preceded by any number of qualifiers,
where a qualifier is a non-private identifier followed by '
- or the empty string (the default name of a library with no library name declaration).
Symbol instances created from the same
name are equal,
but not necessarily identical, but symbols created as compile-time
constants are canonicalized, as all other constant object creations.
assert(new Symbol("foo") == new Symbol("foo")); assert(identical(const Symbol("foo"), const Symbol("foo")));
name is a single identifier that does not start with an underscore,
or it is a qualified identifier,
or it is an operator name different from
then the result of
const Symbol(name) is the same instance that
the symbol literal created by prefixing
# to the content of
would evaluate to.
assert(new Symbol("foo") == #foo); assert(new Symbol("=") == #=]); assert(new Symbol("foo.bar") == #foo.bar); assert(identical(const Symbol("foo"), #foo)); assert(identical(const Symbol("="), #=])); assert(identical(const Symbol("foo.bar"), #foo.bar));
This constructor cannot create a Symbol instance that is equal to
a private symbol literal like
const Symbol("_foo") // Invalid
The created instance overrides Object.==.
The following text is non-normative:
Creating non-const Symbol instances may result in larger output. If
MirrorsUsed from "dart:mirrors" to specify which names
might be passed to this constructor.
const factory Symbol(String name) = internal.Symbol;