Optional<T> class
- Inheritance
-
- Available extensions
Properties
-
first
→ T
-
The first element.
no setterinherited
-
hashCode
→ int
-
Delegates to the underlying value hashCode.
no setteroverride
-
isEmpty
→ bool
-
Whether this collection has no elements.
no setterinherited
-
isNotEmpty
→ bool
-
Whether this collection has at least one element.
no setterinherited
-
isNotPresent
→ bool
-
True when this optional contains no value.
no setter
-
isPresent
→ bool
-
True when this optional contains a value.
no setter
-
iterator
→ Iterator<T>
-
A new
Iterator that allows iterating the elements of this Iterable.
no setteroverride
-
last
→ T
-
The last element.
no setterinherited
-
length
→ int
-
The number of elements in this Iterable.
no setterinherited
-
orNull
→ T?
-
Gets the Optional value, or
null if there is none.
no setter
-
runtimeType
→ Type
-
A representation of the runtime type of the object.
no setterinherited
-
single
→ T
-
Checks that this iterable has only one element, and returns that element.
no setterinherited
-
value
→ T
-
Gets the Optional value.
no setter
Methods
-
any(bool test(T element))
→ bool
-
Checks whether any element of this iterable satisfies
test.
inherited
-
cast<R>()
→ Iterable<R>
-
A view of this iterable as an iterable of
R instances.
inherited
-
contains(Object? element)
→ bool
-
Whether the collection contains an element equal to
element.
inherited
-
elementAt(int index)
→ T
-
Returns the
indexth element.
inherited
-
every(bool test(T element))
→ bool
-
Checks whether every element of this iterable satisfies
test.
inherited
-
expand<T>(Iterable<T> toElements(T element))
→ Iterable<T>
-
Expands each element of this Iterable into zero or more elements.
inherited
-
firstWhere(bool test(T element), {T orElse()?})
→ T
-
The first element that satisfies the given predicate
test.
inherited
-
fold<T>(T initialValue, T combine(T previousValue, T element))
→ T
-
Reduces a collection to a single value by iteratively combining each
element of the collection with an existing value
inherited
-
followedBy(Iterable<T> other)
→ Iterable<T>
-
Creates the lazy concatenation of this iterable and
other.
inherited
-
forEach(void action(T element))
→ void
-
Invokes
action on each element of this iterable in iteration order.
inherited
-
ifAbsent(void ifAbsent())
→ void
-
Execution a function if the Optional value is absent.
-
ifPresent(void ifPresent(T value))
→ void
-
Executes a function if the Optional value is present.
-
join([String separator = ""])
→ String
-
Converts each element to a String and concatenates the strings.
inherited
-
lastWhere(bool test(T element), {T orElse()?})
→ T
-
The last element that satisfies the given predicate
test.
inherited
-
map<T>(T toElement(T e))
→ Iterable<T>
-
The current elements of this iterable modified by
toElement.
inherited
-
noSuchMethod(Invocation invocation)
→ dynamic
-
Invoked when a nonexistent method or property is accessed.
inherited
-
or(T defaultValue)
→ T
-
Gets the Optional value with a default.
-
reduce(T combine(T value, T element))
→ T
-
Reduces a collection to a single value by iteratively combining elements
of the collection using the provided function.
inherited
-
singleWhere(bool test(T element), {T orElse()?})
→ T
-
The single element that satisfies
test.
inherited
-
skip(int count)
→ Iterable<T>
-
Creates an Iterable that provides all but the first
count elements.
inherited
-
skipWhile(bool test(T value))
→ Iterable<T>
-
Creates an
Iterable that skips leading elements while test is satisfied.
inherited
-
take(int count)
→ Iterable<T>
-
Creates a lazy iterable of the
count first elements of this iterable.
inherited
-
takeWhile(bool test(T value))
→ Iterable<T>
-
Creates a lazy iterable of the leading elements satisfying
test.
inherited
-
toList({bool growable = true})
→ List<T>
-
Creates a List containing the elements of this Iterable.
inherited
-
toSet()
→ Set<T>
-
Creates a Set containing the same elements as this iterable.
inherited
-
toString()
→ String
-
Returns a string representation of (some of) the elements of
this.
override
-
transform<S extends Object>(S transformer(T value))
→ Optional<S>
-
Transforms the Optional value.
-
transformNullable<S extends Object>(S? transformer(T value))
→ Optional<S>
-
Transforms the Optional value.
-
where(bool test(T element))
→ Iterable<T>
-
Creates a new lazy Iterable with all elements that satisfy the
predicate
test.
inherited
-
whereType<T>()
→ Iterable<T>
-
Creates a new lazy Iterable with all elements that have type
T.
inherited
