The whole answer for Rails 3, 4 and 5 is: If cache_classes is off (by default it’s off in development, but on in production): Rails.application.eager_load! Then: ActiveRecord::Base.descendants This makes sure all models in your application, regardless of where they are, are loaded, and any gems you are using which provide models are also loaded. This … Read more
Attention: Please see Leo Dabus’ answer for a proper implementation for Swift 4 and Swift 5. Swift 4 or later The Substring type was introduced in Swift 4 to make substrings faster and more efficient by sharing storage with the original string, so that’s what the subscript functions should return. Try it out here extension … Read more
Python’s complaining because the inner set objects are mutable and thus not hashable. The solution is to use frozenset for the inner sets, to indicate that you have no intention of modifying them.
Use of clone() in Java is tricky and questionable1,2. Effectively, clone() is a copy constructor and for that, the Dart List, Map and Set types each have a named constructor named .from() that perform a shallow copy; e.g. given these declarations Map<String, int> numMoons, moreMoons; numMoons = const <String,int>{ ‘Mars’ : 2, ‘Jupiter’ : 27 … Read more
Since Java 8 you can now use streams for that: long[] arr = { 1, 2, 3, 4 }; List<Long> list = Arrays.stream(arr).boxed().collect(Collectors.toList());
b has a capacity of 3, but a size of 0. The fact that ArrayList has some sort of buffer capacity is an implementation detail – it’s not part of the List interface, so Collections.copy(List, List) doesn’t use it. It would be ugly for it to special-case ArrayList. As tddmonkey has indicated, using the ArrayList … Read more
IEnumerable<T> represents a series of items that you can iterate over (using foreach, for example), whereas IList<T> is a collection that you can add to or remove from. Typically you’ll want to be able to modify an Order by adding or removing OrderLines to it, so you probably want Order.Lines to be an IList<OrderLine>. Having … Read more
The method add of Set returns a boolean whether a value already exists (true if it does not exist, false if it already exists, see Set documentation). So just iterate through all the values: public Set<Integer> findDuplicates(List<Integer> listContainingDuplicates) { final Set<Integer> setToReturn = new HashSet<>(); final Set<Integer> set1 = new HashSet<>(); for (Integer yourInt : … Read more
remove() (in Map as well as in Collection) is not generic because you should be able to pass in any type of object to remove(). The object removed does not have to be the same type as the object that you pass in to remove(); it only requires that they be equal. From the specification … Read more
1) If the Map can be immutable: Collections.emptyMap() // or, in some cases: Collections.<String, String>emptyMap() You’ll have to use the latter sometimes when the compiler cannot automatically figure out what kind of Map is needed (this is called type inference). For example, consider a method declared like this: public void foobar(Map<String, String> map){ … } … Read more