DelegatingList<E> class
Creates a List that delegates all operations to a base list.
This class can be used hide non-List methods of a list object,
or it can be extended to add extra functionality on top of an existing
list object.
class DelegatingList<E> extends DelegatingIterable<E> implements List<E> {
DelegatingList(List<E> base) : super(base);
List<E> get _listBase => _base;
E operator [](int index) => _listBase[index];
void operator []=(int index, E value) {
_listBase[index] = value;
}
void add(E value) {
_listBase.add(value);
}
void addAll(Iterable<E> iterable) {
_listBase.addAll(iterable);
}
Map<int, E> asMap() => _listBase.asMap();
void clear() {
_listBase.clear();
}
void fillRange(int start, int end, [E fillValue]) {
_listBase.fillRange(start, end, fillValue);
}
Iterable<E> getRange(int start, int end) => _listBase.getRange(start, end);
int indexOf(E element, [int start = 0]) => _listBase.indexOf(element, start);
void insert(int index, E element) {
_listBase.insert(index, element);
}
void insertAll(int index, Iterable<E> iterable) {
_listBase.insertAll(index, iterable);
}
int lastIndexOf(E element, [int start]) =>
_listBase.lastIndexOf(element, start);
void set length(int newLength) {
_listBase.length = newLength;
}
bool remove(Object value) => _listBase.remove(value);
E removeAt(int index) => _listBase.removeAt(index);
E removeLast() => _listBase.removeLast();
void removeRange(int start, int end) {
_listBase.removeRange(start, end);
}
void removeWhere(bool test(E element)) {
_listBase.removeWhere(test);
}
void replaceRange(int start, int end, Iterable<E> iterable) {
_listBase.replaceRange(start, end, iterable);
}
void retainWhere(bool test(E element)) {
_listBase.retainWhere(test);
}
Iterable<E> get reversed => _listBase.reversed;
void setAll(int index, Iterable<E> iterable) {
_listBase.setAll(index, iterable);
}
void setRange(int start, int end, Iterable<E> iterable, [int skipCount = 0]) {
_listBase.setRange(start, end, iterable, skipCount);
}
void shuffle([Random random]) {
_listBase.shuffle(random);
}
void sort([int compare(E a, E b)]) {
_listBase.sort(compare);
}
List<E> sublist(int start, [int end]) => _listBase.sublist(start, end);
}
Extends
DelegatingIterable<E> > DelegatingList<E>
Implements
Constructors
new DelegatingList(List<E> base) #
Create a wrapper that forwards operations to base.
DelegatingList(List<E> base) : super(base);
Properties
final E first #
Returns the first element.
If this is empty throws a StateError. Otherwise this method is
equivalent to this.elementAt(0)
E get first => _base.first;
final bool isEmpty #
final bool isNotEmpty #
final Iterator<E> iterator #
int get length #
void set length(int newLength) #
Changes the length of this list.
If
newLength is greater than
the current length, entries are initialized to null.
Throws an UnsupportedError if the list is fixed-length.
void set length(int newLength) {
_listBase.length = newLength;
}
final E single #
Returns the single element in this.
If this is empty or has more than one element throws a StateError.
E get single => _base.single;
Operators
E operator [](int index) #
Returns the object at the given index in the list or throws a RangeError if index is out of bounds.
E operator [](int index) => _listBase[index];
Methods
void add(E value) #
Adds value to the end of this list, extending the length by one.
Throws an UnsupportedError if the list is fixed-length.
void add(E value) {
_listBase.add(value);
}
void addAll(Iterable<E> iterable) #
Appends all objects of iterable to the end of this list.
Extends the length of the list by the number of objects in iterable. Throws an UnsupportedError if this list is fixed-length.
void addAll(Iterable<E> iterable) {
_listBase.addAll(iterable);
}
bool any(bool test(E element)) #
Map<int, E> asMap() #
Returns an unmodifiable Map view of this.
The map uses the indices of this list as keys and the corresponding objects
as values. The Map.keys Iterable iterates the indices of this list
in numerical order.
List<String> words = ['fee', 'fi', 'fo', 'fum'];
Map<int, String> map = words.asMap();
map[0] + map[1]; // 'feefi';
map.keys.toList(); // [0, 1, 2, 3]
Map<int, E> asMap() => _listBase.asMap();
void clear() #
Removes all objects from this list; the length of the list becomes zero.
Throws an UnsupportedError, and retains all objects, if this is a fixed-length list.
void clear() {
_listBase.clear();
}
bool contains(Object element) #
E elementAt(int index) #
Returns the indexth element.
If this has fewer than
index elements throws a RangeError.
Note: if this does not have a deterministic iteration order then the
function may simply return any element without any iteration if there are
at least
index elements in this.
E elementAt(int index) => _base.elementAt(index);
bool every(bool test(E element)) #
Iterable expand(Iterable f(E element)) #
Expands each element of this Iterable into zero or more elements.
The resulting Iterable runs through the elements returned by f for each element of this, in order.
The returned Iterable is lazy, and calls f for each element of this every time it's iterated.
Iterable expand(Iterable f(E element)) => _base.expand(f);
E firstWhere(bool test(E element), {E orElse()}) #
Returns the first element that satisfies the given predicate test.
If none matches, the result of invoking the
orElse function is
returned. By default, when
orElse is null, a StateError is
thrown.
E firstWhere(bool test(E element), {E orElse()}) =>
_base.firstWhere(test, orElse: orElse);
dynamic fold(initialValue, combine(previousValue, E element)) #
Reduces a collection to a single value by iteratively combining each element of the collection with an existing value using the provided function.
Use initialValue as the initial value, and the function combine to create a new value from the previous one and an element.
Example of calculating the sum of an iterable:
iterable.fold(0, (prev, element) => prev + element);
fold(initialValue, combine(previousValue, E element)) => _base.fold(initialValue, combine);
void forEach(void f(E element)) #
Iterable<E> getRange(int start, int end) #
Returns an Iterable that iterates over the objects in the range start inclusive to end exclusive.
An error occurs if end is before start.
An error occurs if the
start and
end are not valid ranges at the time
of the call to this method. The returned Iterable behaves like
skip(start).take(end - start). That is, it does not throw exceptions
if this changes size.
List<String> colors = ['red', 'green', 'blue', 'orange', 'pink'];
Iterable<String> range = colors.getRange(1, 4);
range.join(', '); // 'green, blue, orange'
colors.length = 3;
range.join(', '); // 'green, blue'
Iterable<E> getRange(int start, int end) => _listBase.getRange(start, end);
int indexOf(E element, [int start = 0]) #
Returns the first index of element in this list.
Searches the list from index
start to the end of the list.
The first time an object o is encountered so that o == element,
the index of o is returned.
List<String> notes = ['do', 're', 'mi', 're'];
notes.indexOf('re'); // 1
notes.indexOf('re', 2); // 3
Returns -1 if element is not found.
notes.indexOf('fa'); // -1
int indexOf(E element, [int start = 0]) => _listBase.indexOf(element, start);
void insert(int index, E element) #
Inserts the object at position index in this list.
This increases the length of the list by one and shifts all objects at or after the index towards the end of the list.
An error occurs if the index is less than 0 or greater than length. An UnsupportedError occurs if the list is fixed-length.
void insert(int index, E element) {
_listBase.insert(index, element);
}
void insertAll(int index, Iterable<E> iterable) #
Inserts all objects of iterable at position index in this list.
This increases the length of the list by the length of iterable and shifts all later objects towards the end of the list.
An error occurs if the index is less than 0 or greater than length. An UnsupportedError occurs if the list is fixed-length.
void insertAll(int index, Iterable<E> iterable) {
_listBase.insertAll(index, iterable);
}
String join([String separator = ""]) #
Converts each element to a String and concatenates the strings.
Converts each element to a String by calling Object.toString on it. Then concatenates the strings, optionally separated by the separator string.
String join([String separator = ""]) => _base.join(separator);
int lastIndexOf(E element, [int start]) #
Returns the last index of element in this list.
Searches the list backwards from index start to 0.
The first time an object o is encountered so that o == element,
the index of o is returned.
List<String> notes = ['do', 're', 'mi', 're'];
notes.lastIndexOf('re', 2); // 1
If start is not provided, this method searches from the end of the list./Returns
notes.lastIndexOf('re'); // 3
Returns -1 if element is not found.
notes.lastIndexOf('fa'); // -1
int lastIndexOf(E element, [int start]) => _listBase.lastIndexOf(element, start);
E lastWhere(bool test(E element), {E orElse()}) #
Returns the last element that satisfies the given predicate test.
If none matches, the result of invoking the
orElse function is
returned. By default, when
orElse is null, a StateError is
thrown.
E lastWhere(bool test(E element), {E orElse()}) =>
_base.lastWhere(test, orElse: orElse);
Iterable map(f(E element)) #
Returns a lazy Iterable where each element e of this is replaced
by the result of f(e).
This method returns a view of the mapped elements. As long as the returned Iterable is not iterated over, the supplied function f will not be invoked. The transformed elements will not be cached. Iterating multiple times over the the returned Iterable will invoke the supplied function f multiple times on the same element.
Iterable map(f(E element)) => _base.map(f);
E reduce(E combine(E value, E element)) #
Reduces a collection to a single value by iteratively combining elements of the collection using the provided function.
Example of calculating the sum of an iterable:
iterable.reduce((value, element) => value + element);
E reduce(E combine(E value, E element)) => _base.reduce(combine);
bool remove(Object value) #
Removes the first occurence of value from this list.
Returns true if value was in the list, false otherwise.
List<String> parts = ['head', 'shoulders', 'knees', 'toes'];
parts.remove('head'); // true
parts.join(', '); // 'shoulders, knees, toes'
The method has no effect if value was not in the list.
// Note: 'head' has already been removed.
parts.remove('head'); // false
parts.join(', '); // 'shoulders, knees, toes'
An UnsupportedError occurs if the list is fixed-length.
bool remove(Object value) => _listBase.remove(value);
E removeAt(int index) #
Removes the object at position index from this list.
This method reduces the length of this by one and moves all later objects
down by one position.
Returns the removed object.
The
index must be in the range 0 ≤ index < length.
Throws an UnsupportedError if this is a fixed-length list. In that case the list is not modified.
E removeAt(int index) => _listBase.removeAt(index);
E removeLast() #
Pops and returns the last object in this list.
Throws an UnsupportedError if this is a fixed-length list.
E removeLast() => _listBase.removeLast();
void removeRange(int start, int end) #
Removes the objects in the range start inclusive to end exclusive.
The
start and
end indices must be in the range
0 ≤ index ≤ length, and start ≤ end.
Throws an UnsupportedError if this is a fixed-length list. In that case the list is not modified.
void removeRange(int start, int end) {
_listBase.removeRange(start, end);
}
void removeWhere(bool test(E element)) #
Removes all objects from this list that satisfy test.
An object o satisfies
test if test(o) is true.
List<String> numbers = ['one', 'two', 'three', 'four'];
numbers.removeWhere((item) => item.length == 3);
numbers.join(', '); // 'three, four'
Throws an UnsupportedError if this is a fixed-length list.
void removeWhere(bool test(E element)) {
_listBase.removeWhere(test);
}
void replaceRange(int start, int end, Iterable<E> iterable) #
Removes the objects in the range
start inclusive to
end exclusive
and inserts the contents of replacement in its place.
List<int> list = [1, 2, 3, 4, 5];
list.replaceRange(1, 4, [6, 7]);
list.join(', '); // '1, 6, 7, 5'
An error occurs if
start..
end is not a valid range for this.
void replaceRange(int start, int end, Iterable<E> iterable) {
_listBase.replaceRange(start, end, iterable);
}
void retainWhere(bool test(E element)) #
Removes all objects from this list that fail to satisfy test.
An object o satisfies
test if test(o) is true.
List<String> numbers = ['one', 'two', 'three', 'four'];
numbers.retainWhere((item) => item.length == 3);
numbers.join(', '); // 'one, two'
Throws an UnsupportedError if this is a fixed-length list.
void retainWhere(bool test(E element)) {
_listBase.retainWhere(test);
}
void setAll(int index, Iterable<E> iterable) #
Overwrites objects of this with the objects of
iterable, starting
at position
index in this list.
List<String> list = ['a', 'b', 'c'];
list.setAll(1, ['bee', 'sea']);
list.join(', '); // 'a, bee, sea'
This operation does not increase the length of this.
The index must be non-negative and no greater than length.
The iterable must not have more elements than what can fit from index to length.
If iterable is based on this list, its values may change /during/ the
setAll operation.
void setAll(int index, Iterable<E> iterable) {
_listBase.setAll(index, iterable);
}
void setRange(int start, int end, Iterable<E> iterable, [int skipCount = 0]) #
Copies the objects of iterable, skipping skipCount objects first, into the range start, inclusive, to end, exclusive, of the list.
List<int> list1 = [1, 2, 3, 4];
List<int> list2 = [5, 6, 7, 8, 9];
// Copies the 4th and 5th items in list2 as the 2nd and 3rd items
// of list1.
list1.setRange(1, 3, list2, 3);
list1.join(', '); // '1, 8, 9, 4'
The
start and
end indices must satisfy 0 ≤ start ≤ end ≤ length.
If
start equals
end, this method has no effect.
The
iterable must have enough objects to fill the range from start
to end after skipping
skipCount objects.
If iterable is this list, the operation will copy the elements originally
in the range from skipCount to skipCount + (end - start) to the
range start to end, even if the two ranges overlap.
If iterable depends on this list in some other way, no guarantees are
made.
void setRange(int start, int end, Iterable<E> iterable, [int skipCount = 0]) {
_listBase.setRange(start, end, iterable, skipCount);
}
E singleWhere(bool test(E element)) #
Returns the single element that satisfies test. If no or more than one element match then a StateError is thrown.
E singleWhere(bool test(E element)) => _base.singleWhere(test);
Iterable<E> skip(int n) #
Iterable<E> skipWhile(bool test(E value)) #
Returns an Iterable that skips elements while test is satisfied.
The filtering happens lazily. Every new Iterator of the returned
Iterable iterates over all elements of this.
As long as the iterator's elements satisfy
test they are
discarded. Once an element does not satisfy the
test the iterator stops
testing and uses every later element unconditionally. That is, the elements
of the returned Iterable are the elements of this starting from the
first element that does not satisfy
test.
Iterable<E> skipWhile(bool test(E value)) => _base.skipWhile(test);
void sort([int compare(E a, E b)]) #
Sorts this list according to the order specified by the compare function.
The compare function must act as a Comparator.
List<String> numbers = ['one', 'two', 'three', 'four'];
// Sort from shortest to longest.
numbers.sort((x, y) => x.length.compareTo(y.length));
numbers.join(', '); // 'one, two, four, three'
The default List implementations use Comparable.compare if compare is omitted.
List<int> nums = [13, 2, -11];
nums.sort();
nums.join(', '); // '-11, 2, 13'
void sort([int compare(E a, E b)]) {
_listBase.sort(compare);
}
List<E> sublist(int start, [int end]) #
Returns a new list containing the objects from start inclusive to end exclusive.
List<String> colors = ['red', 'green', 'blue', 'orange', 'pink'];
colors.sublist(1, 3); // ['green', 'blue']
If
end is omitted, the length of this is used.
colors.sublist(1); // ['green', 'blue', 'orange', 'pink']
An error occurs if
start is outside the range 0 .. length or if
end is outside the range start .. length.
List<E> sublist(int start, [int end]) => _listBase.sublist(start, end);
Iterable<E> take(int n) #
Iterable<E> takeWhile(bool test(E value)) #
Returns an Iterable that stops once test is not satisfied anymore.
The filtering happens lazily. Every new Iterator of the returned
Iterable starts iterating over the elements of this.
When the iterator encounters an element e that does not satisfy
test,
it discards e and moves into the finished state. That is, it does not
get or provide any more elements.
Iterable<E> takeWhile(bool test(E value)) => _base.takeWhile(test);
List<E> toList({bool growable: true}) #
Set<E> toSet() #
Iterable<E> where(bool test(E element)) #
Returns a lazy Iterable with all elements that satisfy the predicate test.
This method returns a view of the mapped elements. As long as the returned Iterable is not iterated over, the supplied function test will not be invoked. Iterating will not cache results, and thus iterating multiple times over the returned Iterable will invoke the supplied function test multiple times on the same element.
Iterable<E> where(bool test(E element)) => _base.where(test);