Objective-C Fundamentals

Conditional statements
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based on the value of variables or actions of the user and change their behavior or
flow of execution to suit.
Making conditional decisions is a fundamental part of any programming language,
and C is no different.
B.3.1
The if-else statement
The if-else statement is the simplest of the conditional statements. It evaluates a single
Boolean expression and executes one set of statements if it evaluates to true and
another set of statements if it evaluates to false. The general form is as follows:
if (condition) {
statement block 1
} else {
statement block 2
}
The condition can be any Boolean expression. If the expression evaluates to true
(any value other than zero), statement block 1 is executed; otherwise, statement block
2 is executed. No matter which path is selected, execution then proceeds to the first
statement immediately after the if statement.
The following if statement checks to see if the value of variable x holds a value
greater than 10 and prints a different result depending on the result of this comparison.
int x = 45;
if (x > 10) {
NSLog(@"x is greater than 10");
} else {
NSLog(@"x is less than or equal to 10.");
}
The else keyword and associated statement block are optional and don’t need to be
included if you have no statements you wish to execute whenever the specified condition
evaluates to false. The following if statement prints a message only if variable x
is greater than 10.
int x = 45;
if (x > 10) {
NSLog(@"x is greater than 10");
}
In this case where only one statement is required to be executed in a statement
block, it’s not necessary to wrap the statement in curly braces. The semicolon at the
end of the statement is still required, though, because C uses the semicolon to terminate
the current statement rather than a separator between multiple statements, as
in some other languages. The following if statement is identical in function to the
previous one:
int x = 45;
if (x > 10)
NSLog(@"x is greater than 10");