In Objective-C, the if statement is used to execute code based on a certain condition. The general syntax of an if statement looks like this:
if (condition) {
// code to execute if condition is true
}
The condition inside the parentheses can be any expression that evaluates to a Boolean value (i.e. true or false). Here are some examples:
// check if a number is positive
int num = -5;
if (num > 0) {
NSLog(@"%d is positive", num);
}
// check if a string is empty
NSString *str = @"";
if ([str length] == 0) {
NSLog(@"The string is empty");
}
// check if two strings are equal
NSString *str1 = @"hello";
NSString *str2 = @"world";
if ([str1 isEqualToString:str2]) {
NSLog(@"The strings are equal");
}
In addition to the basic if statement, there are also variants that allow you to execute different code depending on whether the condition is true or false. These are the if-else statement and the if-else if-else statement. Here are some examples:
// check if a number is positive, negative, or zero
int num = -5;
if (num > 0) {
NSLog(@"%d is positive", num);
} else if (num < 0) {
NSLog(@"%d is negative", num);
} else {
NSLog(@"%d is zero", num);
}
// check if a number is even or odd
int num = 7;
if (num % 2 == 0) {
NSLog(@"%d is even", num);
} else {
NSLog(@"%d is odd", num);
}
The if statement can also be nested inside another if statement, giving you even more control over the flow of your code. It's important to use proper indentation to make your code readable and easy to follow.