Accessing objects and its properties inside an array of objects in Objective-C

Question

I am new coding in Objective-C and I am trying to figure out how to do the following:

I have a class Company:

@interface Company : NSObject

@property (strong, nonatomic)NSString *companyID;

@property (strong, nonatomic)NSString *companyName;

@end

I am getting a dictionary from a server and just parsing in objects. After that, I am adding these objects in an array (It´s working - no problem here - I got the JSON).

NSMutableDictionary *companyDictionary = [[NSMutableDictionary alloc]initWithDictionary:response];

NSArray *companyArray = [companyDictionary valueForKey:@"data"];
NSMutableArray *companyInformationArray = [NSMutableArray new];

//Parser
for (int i = 0; i < [companyArray count]; i++) {
    Company *company = [Company new];
    company.companyID = [[companyArray objectAtIndex:i] valueForKey:@"company_id"];
    company.companyName = [[companyArray objectAtIndex:i] valueForKey:@"name"];

    [companyInformationArray addObject:company];
}

THE PROBLEM IS: I need to access the objects and its fields inside

companyInformationArray

I am just trying to do something similar with (these two approaching will not work of course):

Company *company = [Company new];
company = [[companyInformationArray objectAtIndex:0] valueForKey:@"name"];

Or:

Company *company = [Company new];
company.companyName = [[companyInformationArray objectAtIndex:0] companyName];

Could you please help me?

Thanks!

A very minor, unrelated observation: It's often prudent to use copy rather than strong for your NSString properties of classes like Company. By using strong, if the string happened to be a NSMutableString and it was mutated later, you risk having your Company object unintentionally mutate, too. By making it copy, you avoid this (admittedly edge-case) scenario. — Rob
– Rob, Commented Jun 23, 2017 at 20:07

Rob · Accepted Answer · 2017-06-23 19:48:27Z

6

Objective-C now supports lightweight generics. For example, rather than a simple NSMutableArray, you can specify that your array is an array of Company objects:

NSMutableArray <Company *> *companyInformationArray;

Then you can do something like:

NSString *nameOfSecondCompany = companyInformationArray[1].companyName;

The virtue of this is that the compiler will warn you if you try to add something that isn't a Company and likewise you enjoy strong typing of the properties without any casting.

answered Jun 23, 2017 at 19:48

Rob

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3 Comments

BSants Over a year ago

Thank you for helping as well. I will keep it in mind.

fullofsquirrels Over a year ago

Nice addition; this is especially useful when Xcode auto-completes enumeration blocks, e.g. instead of [companyInformationArray enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop){}];, you get [companyInformationArray enumerateObjectsUsingBlock:^(Company * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop){}];

Chris Over a year ago

This is a much better option than casting the element at a particular index. Why forego compiler support if you have it?

DonMag · Accepted Answer · 2017-06-23 19:18:10Z

4

Off the top of my head (not running it to test)...

// get the Company object at slot [0] in the array of Company objects
Company *company = (Company *)[companyInformationArray objectAtIndex:0];

// now use the properties...
myNameLabel.text = company.companyName;
myIDLabel.text = company.companyID;

answered Jun 23, 2017 at 19:18

DonMag

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