Switch statements in Objective-C provide a way to execute different parts of code based on the value of a variable or expression. They are particularly useful when you have multiple possible values for a variable and want to execute different code for each value.

1. Switch Statement Structure:

   • The switch statement evaluates an expression and executes the corresponding case block.
   • Each case block ends with a break statement to prevent fall-through.
   • The default case is optional but recommended for handling unexpected values.

2. Syntax:

   switch (expression) {
       case constant1:
           // Code to execute if expression == constant1
           break;
       case constant2:
           // Code to execute if expression == constant2
           break;
       // More cases...
       default:
           // Code to execute if expression doesn't match any case
           break;
   }
   

3. Expression Types:

   • The expression in a switch statement must be an integer or an enumeration type.
   • Floating-point numbers and strings are not allowed.

Let's look at a practical example to understand how switch statements work in Objective-C.

• Expression: dayOfWeek is the variable being evaluated.
• Cases: Each case corresponds to a day of the week.
• Break: Each case ends with a break statement to prevent fall-through.
• Default: The default case handles any unexpected values.

Write a program that evaluates a student's grade and prints the corresponding letter grade.

Requirements:

• A for 90-100
• B for 80-89
• C for 70-79
• D for 60-69
• F for below 60

Solution:

• Expression: score / 10 reduces the score to a single digit.
• Cases: Each case corresponds to a grade range.
• Break: Each case ends with a break statement to prevent fall-through.
• Default: The default case handles scores below 60.

1. Missing Break Statements:

   • Forgetting to include break statements can lead to unintended fall-through, where multiple cases are executed.

2. Invalid Expression Types:

   • Using non-integer types (e.g., floats, strings) in the switch expression will result in a compilation error.

3. Unreachable Code:

   • Placing code after a break statement within a case block will make it unreachable.

• Switch statements provide a clean and efficient way to handle multiple conditions based on the value of an expression.
• Always include break statements to prevent fall-through.
• Use the default case to handle unexpected values.
• Ensure the expression in the switch statement is of an appropriate type (integer or enumeration).

By mastering switch statements, you can write more readable and maintainable code when dealing with multiple conditional branches.