Blackhorse programmer _ objective-C Foundation notes (2)

Nsarray

 

Create nsarray

Nsarray * array = [nsarray arraywithobject: @ "Jack"] create a single element

 

Nsarray * array3 = [nsarray arraywithobjects: @ "Jack", @ "Rose", nil] create multiple elements

 

Quickly create an nsarray object

Nsarray * array4 = @ [@ "Jack", @ "Rose", @ "4324324"]

 

[Array. Count] calculates the number of array elements

 

Array3 [0]

[Array3 objectatindex: 1] elements accessing the Array

 

Note: The OC array cannot store nil values, and nil is the end mark of the array.

The OC array can only store OC objects, but cannot store non-OC object types, such as int, struct, and enum.

Nsarray * array = [nsarray array] This array is always an empty array

 

Traverse Arrays

 

Method 1,

Person *p = [[Person alloc] init];        NSArray *array = @[p, @"rose", @"jack"];           for (int i = 0; i<array.count; i++)       {            NSLog(@"%@", array[i]);       }

 

 

Method 2,

 

Id OBJ represents each element in the array int I = 0; For (id obj in array) {// locate the position of the OBJ element in the array nsuinteger I = [array indexofobject: OBJ]; nslog (@ "% LD-% @", I, OBJ); // I ++; if (I = 1) {break ;}}

 

 

Method 3,

 

 

[Array enumerateobjectsusingblock: // each time an element is traversed, a block is called. // The current element and index position are passed as parameters to the block ^ (id obj, nsuinteger idx, bool * Stop) {nslog (@ "% LD-% @", idx, OBJ); If (idx = 0) {// stop traversal * Stop = yes;}];

 

 

Nsmutablearray

 

Create an array

Nsmutablearray * array = [nsmutablearray arraywithobjects: @ "Rose", @ "Jim", nil]

 

Add Element

[Array addobject: [[person alloc] init];

[Array addobject: @ "Jack"];

 

Delete Element

[Array removeallobjects]

Deletes a specified object.

[Array removeobject: @ "Jack"];

[Array removeobjectatindex: 0];

 

Nsset

 

Create

Nsset * s = [nsset set]

Nsset * S2 = [nsset setwithobjects: @ "Jack", @ "Rose", @ "jack2", @ "jack3", nil]

 

Randomly extract an element

Nsstring * STR = [S2 anyobject];

Nslog (@ "% @", STR );

 

Nsmutableset

 

Nsmutableset * s = [nsmutableset];

Add Element

[S addobject: @ "hack"];

Delete Element

[S removeobject: <# (ID) #>];

 

 

Comparison between nsset and nsarray

1. Commonalities

1) All are collections and can store multiple OC objects.

2) Only OC objects can be stored, not non-OC object types (basic data types: int, Char, float, struct, enumeration)

3) They are both immutable and each has a mutable subclass.

 

2 Differences

Nsarray has sequence, nsset has no sequence

 

Nsdictionary

 

A dictionary is composed of an index (key) and text content (value)

 

Create an unchangeable dictionary

 

Method 1,

Nsdictionary * dict = [nsdictionary dictionarywithobject: @ "Jack" forkey: @ "name"];

Method 2,

Nsarray * keys = @ [@ "name", @ "Address"];

Nsarray * objects = @ [@ "Jack", @ "Beijing"];

Nsdictionary * dict = [nsdictionary dictionarywithobjects: Objects forkeys: Keys];

Method 3,

Nsdictionary * dict = [nsdictionary dictionarywithobjectsandkeys:

@ "Jack", @ "name ",

@ "Beijing", @ "Address ",

@ "32423434", @ "QQ", nil];

Quickly create a dictionary

Nsdictionary * dict =@ {@ "name": @ "Jack", @ "Address": @ "Beijing "};

 

Retrieve a dictionary object

Id OBJ = [dict objectforkey: @ "name"]

 

Quickly retrieve a dictionary object

Id OBJ = dict [@ "name"]

 

Variable dictionary nsmutabledictionary

 

Nsmutabledictionary * dict = [nsmutabledictionary dictionary]

 

Add a key-Value Pair

[Dict setobject: @ "Jack" forkey: @ "name"];

 

Remove a key-Value Pair

[Dict removeobjectforkey: @ "name"];

 

Traverse dictionary

 

Method 1,

 

  NSArray *keys = [dict allKeys];            for (int i = 0; i<dict.count; i++)        {            NSString *key = keys[i];            NSString *object = dict[key];                    NSLog(@"%@ = %@", key, object);        }    

 

Method 2,

 

 

 [dict enumerateKeysAndObjectsUsingBlock:     ^(id key, id obj, BOOL *stop) {         NSLog(@"%@ - %@", key, obj);                  // *stop = YES;     }];

Blackhorse programmer _ objective-C Foundation notes (2)