Index of element in Objective-C

In Objective-C, you can use the indexOfObject: method of an NSArray object to get the index of an element in the array. Here is an example:

Suppose we have an array called myArray that contains some strings:

``objective-c NSArray *myArray = @[@"apple", @"banana", @"cherry", @"date"];



To get the index of the string "cherry" in the array, we can use the indexOfObject: method like this:

objective-c

NSUInteger index = [myArray indexOfObject:@"cherry"];



The indexOfObject: method returns the index of the object in the array, or NSNotFound if the object is not in the array. In this case, the variable index will be set to 2, since "cherry" is at index 2 in the array.
Here is another example that shows how to use the indexOfObject: method to find the index of a custom object in an array:

Suppose we have a class called Person that represents a person with a name and an age, and we have an array called people that contains some Person objects:

objective-c

@interface Person : NSObject
@property (nonatomic, strong) NSString *name;

@property (nonatomic) NSInteger age;
- (instancetype)initWithName:(NSString *)name age:(NSInteger)age;
@end
@implementation Person
- (instancetype)initWithName:(NSString *)name age:(NSInteger)age {

    self = [super init];

    if (self) {

        _name = name;

        _age = age;

    }

    return self;

}
@end
NSArray *people = @[[[Person alloc] initWithName:@"Alice" age:25],

                    [[Person alloc] initWithName:@"Bob" age:30],

                    [[Person alloc] initWithName:@"Charlie" age:35]];



To find the index of the person with name "Bob" in the array, we can use the indexOfObject: method like this:
objective-c

Person *bob = [[Person alloc] initWithName:@"Bob" age:30];

NSUInteger index = [people indexOfObject:bob];

The indexOfObject: method uses the isEqual: method of Person objects to compare them, so we need to make sure that the isEqual: method is properly implemented in the Person` class for this to work correctly.

Index of element in Objective-C

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