What is decision making in Objective-C?
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
xwith a default value50. - Lines 8 and 9: We use the
if-elseblock to check whether the value of x is greater than20or 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
xis less than20, 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
50as the default value. - Line6: We use a ternary operator to print whether the value of
xis greater than20or 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 blockbreak;// condition blockdefault:// 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
Fis compared withA. It results in a false, and the next case statement is executed. - Line 13: We have our second case where
Fis equal tocase 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.
