The difference between Nsset and Nsarray

 the difference between Nsset and Nsarray 

Nsset exactly what type, in fact it and nsarray functional nature, for storing objects, belong to the collection; Nsset, Nsmutableset class declares programming interface objects, unordered collections, which are stored in memory in a discontinuous way, unlike Nsarray, Nsdictionary (all ordered collections) class declares that the programming interface object is an ordered set, where the memory location is contiguous;

Nsset and our Common Nsarry difference is: In the search for an element nsset more efficient than nsarray, mainly because it uses an algorithm hash (hash, can also be translated as a hash); The development documentation explains this: you can use sets as an Alternative to arrays when the order of elements isn ' t important and performance in testing whether a object is contained The set is a consideration-while arrays was ordered, testing for membership was slower than with sets.

For example, if you want to store element A, a hash algorithm can directly find the location where a should be stored, and also, when you want to access a, a hash process can find the location of a storage. For Nsarray, if you want to know if a is not in the array, you need to facilitate the entire array, obviously less efficient;

Nsset,nsarray are classes, you can add only cocoa objects, and if you need to include basic data types (int,float,bool,double, etc.), you need to encapsulate the data into a nsnumber type.

Summary of common methods of Nsset

+ (ID) setwithobjects:obj1,obj2,... nil	Create a new collection with a set of objects
-(ID) initwithobjects:obj1,obj2,.... nil	Initializes a newly allocated collection with a set of objects
-(Nsuinteger) Count	Returns the number of members of a collection
-(BOOL) containsobject:obj	Determines whether the collection contains object obj
-(BOOL) member:obj	Determines whether the collection contains object obj
-(nsenumerator*) Objectenumerator	Returns all objects in the collection to an object of type Nsenumerator
-(BOOL) Issubsetofset:nsset	Determines whether a collection is a subset of Nsset
-(BOOL) Intersectsset:nsset	Determines whether the intersection of two sets has at least one element
-(BOOL) Isequaltoset:nsset	Determines whether two sets are equal

Summary of common methods of Nsmutableset

-(ID) setwithcapcity:size	To create a new collection with size sizes
-(ID) initwithcapcity:size	Initializes a newly allocated collection of size
-(void) addobject:obj	Add Object obj to the collection
-(void) removeobject:obj	To delete an object from the collection obj
-(void) removeallobjects	Delete all objects in the collection
-(void) Unionset:nsset	Add all elements of Nsset to the collection
-(void) Minusset:nsset	Remove all nsset elements from the collection
-(void) Interectset:nsset	Set and Nsset do intersection operations

The difference between Nsset and Nsarray