Basic of Arrays - Objective C

Objective C programming language provides a data structure called the array, which can store a fixed-size sequential collection of elements of the same type.An array is used to store a collection of data, but it is often useful to think of an array as a collection of variable of the same type.

Instead of declaring individual variables, such as number0,number1,...and number99, you declare one array variable such as numbers and use number[0],number[1], and ...number[99] to represent individual variables. A specific in an array is accessed by an index.

An array consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.

---

Declaring Arrays

To declare an array in objective C programmer specifies the type of the elements and the number of element required by an array as follows:

type arrayName [arraysize];

This is called a single dimensional array. The arraySize must be an integer constant greater than zero and type can be any valid objective C data type. For example, to declare a 10 element array called balance of type double, use this statement.

double balance [10];

Now, balance is a variable array which is sufficient to hold up to 10 double numbers.

---

Initializing Arrays

You can initialize an array in objective C either one by one or using a single statement as follows;

double balance[5] =  {1000.0 , 2.0 ,3.4, 17.0 ,50.0};

The number of values between braces { } can not be larger than the number of element that we declare for the array between square bracket[]. Following is an example to assign a single element of the array.
If you omit the size of the array, an array just big enough to hold the initialization is created. Therefore, if you write:

double balance[ ] =  {1000.0 , 2.0 ,3.4, 17.0 ,50.0};

You will create exactly the same array as you did in the previous example

double balance[4] =  50.0;

The above statement assign element number 5th in the array a value of 50.0. Array with 4th index will be 5th, i.e., last element because all array have 0 as the index of their first element which is also called base index. Following is the pictorial representation of the same array we discussed above:


Accessing  Array Element
An element is accessed by indexing the array name. This is done by placing the index of the element within square brackets after the name of the array.For example,

double salary =  balance[9];

The above statement will take 10th element from the array and assign the value to salary variable. Following is an example, which will use all the above mentioned three concept viz.,declaration,assignment and accessing arrays.

#import <Foundation/Foundation.h>
int main()
{
    int n[10];          // n is an array of 10 integers
    int i,j;
   
//initialize element of array n t 0
    for ( i = 0; i<10; i++)
    {
            n[i] = i +100;  //set element at location 1 to 1 + 100
   }
 
  //output each array element's values
   for(  j = 0 ;j<10; j++)
  {
     NSLog(@"Element[%d] = %d\n" , j, n[j] );
  }
return 0;
}