Passing Arguments and Return Values
There are two ways of passing arguments to a function, By value and By reference.
- Passing by value means that a copy of the argument is passed to the function, so any changes made to the argument within the function do not affect the original value.
- Passing by reference means that a pointer to the argument is passed to the function, so any changes made to the argument within the function affect the original value.
By default, Objective-C passes arguments by value. To pass an argument by reference, we use an asterisk (*) before the parameter name in both the function declaration and definition. We also use an ampersand (&) before the argument name when calling the function.
For example, the following code defines and calls a function called swap that swaps two integers by passing them by reference:
ObjectiveC
// Objective-C program to pass arguments// and return values#include <stdio.h>// Function declarationvoid swap(int *x, int *y);// Function definitionvoid swap(int *x, int *y){ int temp; // temp gets the value pointed by x temp = *x; // x gets the value pointed by y *x = *y; // y gets the value stored in temp *y = temp; }// Driver codeint main(){ // Function call int a = 10; int b = 20; printf("Before swap: a = %d, b = %d\n", a, b); swap(&a, &b); printf("After swap: a = %d, b = %d\n", a, b); return 0;} |
Output:
Function Returning Value
A function can return only one value to its caller. The return type of a function must match the type of value returned by it. To return a value from a function, we use the return keyword followed by the value or expression to be returned.
For example, the following code defines and calls a function called square that returns the square of an integer:
ObjectiveC
// Auther: Nikunj Sonigara#include <stdio.h>// Function declarationint square(int x);// Function definitionint square(int x){ return x * x; // return the square of x}int main(){ // Function call int a = 5; int b = square(a); printf("The square of %d is %d\n", a, b); return 0;} |
Output:
Function Not Returning Value
Some functions do not return any value to their caller. In this case, the return type of the function is the keyword void. A function with a void return type can use the return keyword without any value to exit the function.
For example, the following code defines and calls a function called printHello that prints “Hello, world!” to the standard output and does not return any value:
C++
// Auther: Nikunj Sonigara#include <stdio.h>// Function declarationvoid printHello(void);// Function definitionvoid printHello(void){ printf("Hello, world!\n"); return; // optional, as it's not needed here}int main(){ // Function call printHello(); // prints "Hello, world!" return 0;} |
Output:
Functions in Objective-C
Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It is the main programming language used by Apple for the OS X and iOS operating systems and their respective application programming interfaces (APIs), Cocoa and Cocoa Touch.
One of the features of Objective-C is that it supports functions, which are named blocks of code that can be called upon to perform a specific task. Functions can be provided with data on which to perform the task and can return a result to the code that called them. Functions can help to organize the code, avoid repetition, and improve readability and maintainability.