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Dart – Common Collection Methods

  • Difficulty Level : Easy
  • Last Updated : 30 Aug, 2020

List, Set, and Map share common functionality found in many collections. Some of this common functionality is defined by the Iterable class, which List and Set implement.

1. isEmpty() or isNotEmpty:

Use isEmpty or isNotEmpty to check whether a list, set, or map has items:

Example:

Dart




void main(){
    
var coffees = [];
var teas = ['green', 'black', 'chamomile', 'earl grey'];
print(coffees.isEmpty);
print(teas.isNotEmpty);
}

Output:

true
true

2. forEach():

To apply a function to each item in a list, set, or map, you can use forEach():

Example:

Dart




void main(){
    
    
var teas = ['green', 'black', 'chamomile', 'earl grey'];
  
var loudTeas = teas.map((tea) => tea.toUpperCase());
loudTeas.forEach(print);
}

Output:

GREEN
BLACK
CHAMOMILE
EARL GREY

3.where():

Use Iterable’s where() method to get all the items that match a condition. Use Iterable’s any() and every() methods to check whether some or all items match a condition.

Example:

Dart




void main(){
    
var teas = ['green', 'black', 'chamomile', 'earl grey'];
  
// Chamomile is not caffeinated.
bool isDecaffeinated(String teaName) =>
    teaName == 'chamomile';
  
// Use where() to find only the items that return true
// from the provided function.
  
  
// Use any() to check whether at least one item in the
// collection satisfies a condition.
print(teas.any(isDecaffeinated));
  
// Use every() to check whether all the items in a
// collection satisfy a condition.
print(!teas.every(isDecaffeinated));
}

Output:

true
true

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