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What is decision making in Objective-C?

Salman Yousaf

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

Overview

The programmer must define one or more criteria to be evaluated or tested by the program. They should also be mindful about a statement(s) to be performed if the condition is found to be true/false, and optionally, further statements to be run if the condition is found to be true/false.

Any non-zero and non-null values are presumed to be true in the Objective-C programming language, whereas zero and null values are believed to be false. Some assertion operators are used to calculate them. These assertions can be if, if-else, nested if, switch, or ternary operator.

1. The if-else statement

The if-else or nested if-else blocks in Objective-C are used for decision-making. Let's elaborate on a real-world example:

Syntax

if (condition) {
/* code block */
}
else {
/* ----other conditions---- */
}

Code example

In the code below, we check whether the value of x variable is greater than 20 or not. Then we print a message on the console accordingly.

#import <Foundation/Foundation.h>
int main() {
NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
/* define an integer x with 50 value */
int x = 50;
/* used if to check a condition*/
if( x > 20 ) {
NSLog(@"x is greater than 20\n" );
} else {
NSLog(@"x is not greater than 20\n" );
}
[pool drain];
return 0;
}

Code explanation

  • Line 6: We define a variable x with a default value 50.
  • Lines 8 and 9: We use the if-else block to check whether the value of x is greater than 20 or not. If the value of x is greater than 20, then we print "x is greater than 20" .
  • Lines 10 and 11: If the value of x is less than 20, it prints "x is not greater than 20" in the else block.

2. Ternary operator

We can also use the ternary operator as a comparison operator in objective-C to compare values and make decisions.

Syntax

Condition ? condition: text

Code example

In the code below, we implement the ternary operator in Objective-C with a real example:

#import <Foundation/Foundation.h>
int main() {
NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
int x = 50;
x > 20 ? NSLog(@"x is greater than 20\n" ) : NSLog(@"x is less than 20\n");
[pool drain];
return 0;
}

Code explanation

  • Line 5: We declare and define a variable of integer type with 50 as the default value.
  • Line6: We use a ternary operator to print whether the value of x is greater than 20 or not.

3. The Switch statement

The switch statement is used to make decisions just like the if-else or ternary operator.

Syntax

Switch(variable) {
case :
// condition block
break;
// condition block
default:
// default code to execute block
}

Code example

In the code below, we have switch statements to print the grade of a student.

#import <Foundation/Foundation.h>
int main() {
NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
/* define an character with default F */
char grade = 'F';
/* Using switch statement */
switch (grade) {
case 'A':
NSLog(@"Your grade is A");
break;
case 'F':
NSLog(@"Your grade is F, Try again");
break;
default:
NSLog(@"Incorrect information");
}
[pool drain];
return 0;
}

Code explanation

  • Line 7: We declare a character variable initialized to F.
  • Line 10: We have our first case where F is compared with A. It results in a false, and the next case statement is executed.
  • Line 13: We have our second case where F is equal to case F. Hence, it prints a statement, "Your grade is F, Try again".
  • Line 16: The default statement will be executed when no one becomes true.

RELATED TAGS

objective-c

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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