如何对自定义NSArray排序？

Question

I have a class officeSupply

@interface OfficeSupply : NSObject

@property (nonatomic, strong) NSString *itemName;
@property (nonatomic) int total;
@property (nonatomic) int price;
@property (nonatomic) int quantity;
@property (nonatomic, strong) UITextField *quantityText;
@property (nonatomic, strong) UIImage *itemPic;

-(id)initWithName:(NSString *)itemName total:(int)total price:(int)price quantity:(int)quantity picture:(UIImage *)itemPic;

@end

And in my view I have

 OfficeSupply *item1 = [[OfficeSupply alloc] initWithName:@"Stapler" total:0 price:50 quantity:0 picture:[UIImage imageNamed:@"stapler.jpg"]];
OfficeSupply *item2 = [[OfficeSupply alloc] initWithName:@"Paper" total:0 price:150 quantity:0 picture:[UIImage imageNamed:@"101291.jpg"]];
OfficeSupply *item3 = [[OfficeSupply alloc] initWithName:@"Pen" total:0 price:45 quantity:0 picture:[UIImage imageNamed:@"pen.jpg"]];
_items =[NSArray arrayWithObjects:item1, item2, item3, nil];

[_items sortedArrayUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"itemName" ascending:YES selector:@selector(caseInsensitiveCompare:)]]];

I've looked up the problem already but haven't been able to solve my problem.

The last line is supposed to sort it but I don't know why it won't.

I just want to sort them by name.. Any ideas?

Answer 1

您无法编辑NSArray因为它是不可变的，因此您需要执行以下操作：

_items = [_items sortedArrayUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"itemName" ascending:YES selector:@selector(caseInsensitiveCompare:)]]];

Answer 2

The call to sortedArrayUsingDescriptors: returns an NSArray instance, which is the sorted representation of the instance you call the method on. So:

NSArray *sortedItems = [_items sortedArrayUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"itemName" ascending:YES selector:@selector(caseInsensitiveCompare:)]]];

You could also simply further by using literal syntax for your array of sort descriptors.

NSArray *sortedItems = [_items sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"itemName" ascending:YES selector:@selector(caseInsensitiveCompare:)]]];

If you want to keep mutating the _items NSArray instance then create is as an NSMutableArray to start with.

// Make sure _items instance variable is declared as an NSMutableArray    
_items =[NSMutableArray arrayWithObjects:item1, item2, item3, nil];

[_items sortUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"itemName" ascending:YES selector:@selector(caseInsensitiveCompare:)]]];

Answer 3

TAke _items as NSMutableArray...

NSArray *sortedArray;
sortedArray=[_items sortedArrayUsingDescriptors:[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"itemName" ascending:YES selector:@selector(caseInsensitiveCompare:)]]];

[_items removeAllObjects];
[_items addObjectsFromArray:sortedArray];