1. A brief introduction to arrays
1. The array is an object, a collection of object addresses of any type. The OC array can store objects of different types.
The array can only store objects, and cannot store simple data types (int, float, NSInteger...) unless it is used to turn a simple data type into an object through some means. Arrays in C language can save any type of data.
3. The memory stored is continuous
2. Immutable arrays
0. Define an array
//Define an empty arrayNSArray *array1 = [NSArray array] ; array1 = @[];//Empty array//Create an array by specifying an objectarray1 = [[NSArray alloc]initWithObjects:@"123",@"hello",@"ya",@"yuan",@"zi", nil] ; //Create an array in a simple wayarray1 = @[@"123",@"hello",@"ya",@"yuan",@"zi"] ;
1.Length of array
NSInteger count = ; NSLog(@"%ld",count) ;
2. Determine whether the current array contains the corresponding object.
BOOL isHave = [array1 containsObject:@"123"] ;
if (isHave) {
NSLog(@"exist") ;
}else{
NSLog(@"Not exists") ;
}
/*
[A isKindOfClass:B], determine whether Class A is a subclass of B or this class.
[A isMemberOfClass:B], determine whether Class A is Class B (excluding subclasses)
*/
3. Get the last object in the array
NSString *str = [array1 lastObject]; NSLog(@"str=%@",str) ;
4. Get the first object
NSString *str1 = [array1 firstObject]; NSLog(@"str1=%@",str1) ;
5. Take out the specified object of the array (the subscript must be smaller than the count of the array)
NSString *str2 = [array1 objectAtIndex:3] ; NSLog(@"str2=%@",str2) ;
6. Get the position of the specified element in the array If the element does not exist, print the -1 value
int index = (int)[array1 indexOfObject:@"yayuanzi"] ; int index1 = (int)[array1 indexOfObject:@"ya"] ; NSLog(@"index=%d,index=%d",index,index1) ;
7. Array traversal-> Find every element in the array
7.1 Basic for loops are searched one by one through subscripts
for (int i = 0; i < ; i++) {
NSString *str3 = [array1 objectAtIndex:i] ;
NSLog(@"str3 = %@",str3) ;
}
7.2 for in Quick Traversal Note: The types of elements in the array need to be consistent
for (NSString *str4 in array1) {
NSLog(@"str4 = %@",str4) ;
}
8. Convert all elements in the array into strings
[array1 componentsJoinedByString:@“String added between two elements”];
9. Take out some elements in the array
//Only initialize one indexNSIndexSet *indexSet = [NSIndexSet indexSetWithIndex:2]; //The subscript is 1 and the length is 2NSRange range = NSMakeRange(0, 3); //Construct a scope indexindexSet = [NSIndexSet indexSetWithIndexesInRange:range]; [array objectsAtIndexes:indexSet];
10. Write array to file
[array1 writeToFile:path atomically:YES];
11. Read array from file
[NSArray arrayWithContentsOfFile:path];
3. Variable arrays
When the data is uncertain or changes dynamically, variable arrays are needed
0. Create an empty variable array
NSMutableArray *mutArray = [[NSMutableArray alloc]init] ; NSMutableArray *mutArray1 = [NSMutableArray array];
1. Create an array with objects
1. There can only be one object in the initialization
NSMutableArray arrayWithObject:@"111"];
2. There can only be multiple objects in the initialization
2.1[NSMutableArray arrayWithObjects:@"1111",@"222",@"333",@"4444", nil];
2.2[[NSMutableArray alloc] initWithObjects:<#(id), ...#>, nil];
2. Add objects. Pay attention to the differences between the following two types.
NSMutableArray *mutArray = [[NSMutableArray alloc]init] ; Person *personName1 = [[Person alloc]initWithName:@"wuhu"] ; Person *personName2 = [[Person alloc]initWithName:@"yayuanzi"] ; Person *personName3 = [[Person alloc]initWithName:@"company"] ; NSArray *arr = [NSArray arrayWithObjects:personName2,personName3, nil] ; //1.Add objects Pay attention to the differences between the following two types[mutArray addObject:personName1] ; NSLog(@"mutArray = %@",mutArray) ; [mutArray addObject:arr] ; //Add arr as a whole to the arrayNSLog(@"mutArray = %@",mutArray) ; [mutArray addObjectsFromArray:arr] ; //Add objects in arr to a variable array one by oneNSLog(@"mutArray = %@",mutArray) ;
3. The position of the exchange element is based on the subscript
[mutArray exchangeObjectAtIndex:1 withObjectAtIndex:2] ;
4. Delete elements
//4.1 Delete all elements[mutArray removeAllObjects] ; //4.2 Delete the last element[mutArray removeLastObject] ; //4.3 Delete the specified element[mutArray removeObject:personName3] ; //4.4 Delete according to the subscript: Note that the number of elements in the element subscript problem will cause failure[mutArray removeObjectAtIndex:2] ;
Summarize
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