Objective-C string arrays

Question

I have a string array as such:

NSArray *names;
names = [NSArray arrayWithObjects:
@"FirstList",
@"SecondList",
@"ThirdList",
  nil];

I'm trying to assign an element of this string array to a string variable as such:

NSString *fileName = names[0]; // "Incompatible types in initialization"

or with casting

NSString *fileName = (NSString)names[0]; // "Conversion to non-scalar type requested"

I'm trying to do this, so I can use the string in a method that takes a string as an argument, such as:

NSString *plistPath = [bundle pathForResource:filetName ofType:@"plist"];

Is there no way to assign an element of a string array to a string variable?

Update from 2014: The code in this post actually would work these days since special syntactic support has been added to the framework and compiler for indexing NSArrays like `names[0]`. But at the time this question was asked, it gave the error mentioned in this question.

Catfish_Man · Accepted Answer · 2011-04-01 20:47:24Z

8

You don't use C array notation to access NSArray objects. Use the -objectAtIndex: method for your first example:

NSString *fileName = [names objectAtIndex:0];

The reason for this is that NSArray is not "part of Objective-C". It's just a class provided by Cocoa much like any that you could write, and doesn't get special syntax privileges.

answered Apr 1, 2011 at 20:47

Catfish_Man

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3 Comments

Namhcir Over a year ago

Thank you Catfish_Man. What does 'not "part of Objective-C" ' mean, if it is provided by Cocoa?

Catfish_Man Over a year ago

Objective-C is a language, like C++ or Java. Cocoa is a library, like .NET or the STL. Cocoa is written in Objective-C, and usable in Objective-C code, but it is not the same thing as Objective-C.

Sherm Pendley Over a year ago

Also, because Objective-C doesn't provide operator overloading, Cocoa's collection classes can't provide [] support the way STL's std::vector (for example) does.

BoltClock · Accepted Answer · 2011-04-01 20:48:20Z

5

NSArray is a specialized array class unlike C arrays. To reference its contents you send it an objectAtIndex: message:

NSString *fileName = [names objectAtIndex:0];

If you want to perform an explicit cast, you need to cast to an NSString * pointer, not an NSString:

NSString *fileName = (NSString *)[names objectAtIndex:0];

answered Apr 1, 2011 at 20:48

BoltClock

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Comments

user454322 · Accepted Answer · 2014-01-28 04:50:44Z

0

With the new Objective-C literals is possible to use:

NSString *fileName = names[0];

So your code could look like this:

- (void)test5518658
{

 NSArray *names  = @[
         @"FirstList",
         @"SecondList",
         @"ThirdList"];

 NSString *fileName = names[0];

 XCTAssertEqual(@"FirstList", fileName, @"Names doesn't match ");

}

Check Object Subscripting for more information.

answered Jan 28, 2014 at 4:50

user454322

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Objective-C string arrays

Update from 2014: The code in this post actually would work these days since special syntactic support has been added to the framework and compiler for indexing NSArrays like `names[0]`. But at the time this question was asked, it gave the error mentioned in this question.

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Update from 2014: The code in this post actually would work these days since special syntactic support has been added to the framework and compiler for indexing NSArrays like names[0]. But at the time this question was asked, it gave the error mentioned in this question.

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Update from 2014: The code in this post actually would work these days since special syntactic support has been added to the framework and compiler for indexing NSArrays like `names[0]`. But at the time this question was asked, it gave the error mentioned in this question.