OC-NSArray

The array can only store objects, not basic data types
Cannot store nil nil is used to mark the end of the array

Initialization

NSArray *array = [NSMutableArray array];
NSArray *array = [NSArray arrayWithObjects:@"123",@2,@"wf"];

[NSNull null]null object

NSArray *array = [NSArray arrayWithObjects:[NSNull null],[NSNull null],[NSNull null],nil];
NSLog(@"%@",array);//"","",""

Add

[array addObject:@"1"];

[array addObjectsFromArray:@[@"2",@"3"]];]

Insert

[array insertObject:@“0” atIndex:0];

Delete

Delete the specified object
[array removeObject:@“2”];
Delete the last item
[array removeLastObject];
Delete the object under the specified index
[array removeObjectAtIndex:1];
Delete subarray
[array removeObjectsInArray:@[@"0",@"1"]];
Replace the object in the array according to the index
[array replaceObjectAtIndex:1 withObject:@"a"];
Exchange objects under two indices
[array exchangeObjectAtIndex:0 withObjectAtIndex:2];
Override Array
[array setArray:@[@"a",@"b",@"c"]];//Equal to the original array does not exist, and a new array is replaced

Enumeration type

This kind can only choose one
typedef NS-ENUM(NSUInteger,CustomType)
{
ONE,
TWO,
THREE,
};
This can be multiple choices
typedef NS-OPTIONS(NSUInteger,CustomType)
{
ONE =0,
TWO =1<<0,//1
THREE =1<<1,//2 Because of this enumeration, multiple selection will notOverwrite the last selection
};
When multiple selections are made, use | connect such as ONE | TWO

Common methods

Get the first element in the array
array.firstObject
Get the last element of the array
array.lastObject
Get the specified index subscript in the array
array[1]
Determine if the array contains an item
-(BOOL)contatinsObject:(ObjectType)anObject;
If you want to determine your own definition, you need to rewrite the class -(BOOL)isEqual:(id)object
ArrayEnumeration
for(NSString *string in array)
{
NSLog(@“%@”,string);
}
Send a message to each object in the array
[array makeObjectsPerformSelector:@selector(test)];
Return the index value according to the object
[array indexOfObject:@"c"];
Append the object after the immutable array
[array arrayByAddingObject:@""d"];

Sort

sortedArrayUsingSelector

Sort the array of custom objects
[array sortedArrayUsingSelector:@selector(compareAge:)]//This compareAge method needs to be declared and implemented

sortedArrayUsingComparator sorts the array of custom objects by block

Check it out for yourself