#nsmutablearray

久々の更新です。

一次元の配列の並び替えの情報はいくらでもあるのですが、配列を配列化している場合、その２次側の配列の2番目の要素を元に並び替えたいという様なのってあまり無かったのでUPします。

元ネタは、StackOverflowにありました。ありがとうございます！

単純なので、ソースだけ公開します。

- (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. //一次元配列を作成 NSArray *one = @[@"one", @"two", @"three", @"1"]; NSArray *two = @[@"one", @"two", @"three", @"2"]; NSArray *three = @[@"one", @"two", @"three", @"3"]; //これが元になる二次元配列 NSArray *array = [NSMutableArray arrayWithObjects:three,two,one, nil]; //順番の確認 NSLog (@"**** Before *****"); for (NSArray *number in array){ //最後の数字だけ表示する NSLog (@"number=%@",number[3]); } array = [array sortedArrayUsingComparator:^(id a, id b) { NSString *numA = [a objectAtIndex:3]; NSString *numB = [b objectAtIndex:3]; return [numA compare:numB]; }]; //順番の確認 NSLog (@"**** After *****"); //順番の確認 for (NSArray *number in array){ //最後の数字だけ表示する NSLog (@"number=%@",number[3]); } }

実行結果

Ví dụ ta có một NSMutableSet, trong đó chứa một NSMutableArray

NSMutableSet *set1 = [NSMutableSet new]; NSMutableArray *arrayA = [@[@1,@2] mutableCopy]; [set addObject:arrayA]; NSLog(@"%@",set1); // Output: (1,2)

Giờ ta thêm vào một NSMutableArray giống y hệt NSMutableArray trong set1.

NSMutableArray *arrayB = [@[@1,@2] mutableCopy]; [set1 addObject:arrayB]; NSLog(@"%@",set1); // Output: (1,2)

set1 giờ vẫn chỉ chứa 1 object, do object thêm vào giống với object đã có trong set1. Giờ ta thêm vào một NSMutableArray không giống với array có trong set1:

NSMutableArray *arrayC = [@[@1] mutableCopy]; [set1 addObject: arrayC]; NSLog(@"%@",set1); // Output: (1) , (1,2)

Giờ set1 đã chứa 2 array. Nếu ta thay đổi array mới thêm vào giống y hệt array cũ:

[arrayC addObject:@2]; NSLog(@"%@",set1); // Output: (1,2) , (1,2)

Giờ thì set1 lại có 2 array giống hệt nhau. Bản chất của NSSet không cho phép điều này xảy ra, nhưng nó không thể duy trì được khi ta thay đổi một object mà đã có sẵn ở trong NSSet. Kỳ lạ hơn là khi chúng ta copy set1:

NSSet *set2 = [set1 copy]; NSLog(@"%@",set2); // Output: (1,2)

Chúng ta có thể nghĩ là set2 sẽ chứa 2 object như set1. Nhưng không, nó chỉ chứa một, như thể là set2 đã được tạo bằng cách tạo ra một NSSet rỗng rồilần lượt thêm từng phần tử của set1.

Kết luận:

How to: Join an Array in Objective-C

Join an Array in Objective-C

I’m looking for a method of turning a NSMutableArray into a string. Is there anything on a par with this Ruby array method?

>> array1 = [1, 2, 3] >> array1.join(',') => "1,2,3"

Cheers!

Answer: Join an Array in Objective-C

NSArray *array1 = [NSArray arrayWithObjects:@"1", @"2", @"3", nil]; NSString *joinedString = [array1 componentsJoinedByString:@","];

componentsJo…

Fixed How do I convert NSMutableArray to NSArray? #dev #it #asnwer

How do I convert NSMutableArray to NSArray?

How do I convert NSMutableArray to NSArray in objective-c?

Answer: How do I convert NSMutableArray to NSArray?

An NSMutableArray is a subclass of NSArray so you won’t always need to convert but if you want to make sure that the array can’t be modified you can create a NSArray either of these ways depending on whether you want it autoreleased or not:

/…

Hi there. Here's one more tiny but helpful tip from my Swift experience.

In my relatively big Swift project I have to use Foundation framework classes, which sometimes causes certain issues. Today I'll tell you about one of those issues and the solution to it.

Suppose we have a variable of NSMutableArray type and we need to convert it into, say, Swift array with strings. Apparently the code should look like:

var nsArray = NSMutableArray() ... var swiftArray = nsArray as [String]

However, the compiler won't accept it: 'String' is not identical to 'AnyObject'

To resolve this, write the code as:

var nsArray = NSMutableArray() ... var swiftArray = nsArray as AnyObject as [String]

Voila! Now we can work with such arrays like with any ordinary Swift array.

The same issue occurs (and the same solution can be applied) when converting NS(Mutable)Dictionary into Swift dictionary.

Inserting object at index 0 uses the circular buffer magic to put the newly inserted object at the end of the buffer [...] This is fantastic news! It means that __NSArrayM can be processed from either side. You can use __NSArrayM as either stack or queue without any performance hits.

Adding objects to arrays can be fun, but first make sure you have the right kind of array. If you are wanting to add objects to an NSArray, you are not going to have much luck. NSArray's are a fixed length, so you cannot add or insert objects into one.

What you are looking for, good sir, is our friend NSMutableArray.

NSMutableArray *myArray = [[NSMutableArray alloc] init];

Once you have an instance of NSMutableArray, you will have access to fun methods like addObject and insertObject:atIndex.

If you are simply wanting to add an object to the end of your array, this will do the trick:

[myArray addObject:someObject];

Or maybe you want to do something a little fancier. Perhaps you want to add an object to the front of the array. That is as simple as inserting it at the first position in the array, like so:

[myArray insertObject:someObject atIndex:0];

This is how I managed to store and retrieve NSArray or NSMutableArray in Core Data: