Variable declaration using var in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an integer variable named age using var.

Go

var age [1]

Drag options to blanks, or click blank then click option'

Afloat64

Bstring

Cbool

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong type like string or bool for an integer variable.

The var keyword declares a variable. Here, age is declared as an int type.

2fill in blank

medium

Complete the code to declare a string variable named name using var.

Go

var name [1]

Drag options to blanks, or click blank then click option'

Astring

Bint

Cfloat64

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or bool instead of string.

The variable name should hold text, so its type is string.

3fill in blank

hard

Fix the error in the variable declaration to declare a boolean variable named isActive.

Go

var isActive [1]

Drag options to blanks, or click blank then click option'

Abool

Bstring

Cint

Dfloat64

Attempts:

3 left

💡 Hint

Common Mistakes

Using string or int instead of bool.

The variable isActive should be a boolean, so its type is bool.

4fill in blank

hard

Fill both blanks to declare a float variable named price and assign it the value 9.99.

Go

var price [1] = [2]

Drag options to blanks, or click blank then click option'

Afloat64

B9.99

Cint

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using int type for decimal numbers.

Assigning a boolean value instead of a number.

The variable price is declared as float64 to hold decimal numbers and assigned the value 9.99.

5fill in blank

hard

Fill all three blanks to declare a variable named count of type int and assign it the value 10.

Go

var [1] [2] = [3]

Drag options to blanks, or click blank then click option'

Acount

Bfloat64

C10

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name or type.

Assigning a float value to an int variable.

The variable count is declared as an int and assigned the value 10.

Practice

1. What does the var keyword do in Go?

easy

A. Starts a loop

B. Creates a function

C. Imports a package

D. Declares a variable with a name and type

Solution

1. Step 1: Understand the role of var

   The var keyword is used to declare variables in Go, giving them a name and a type.

2. Step 2: Differentiate from other keywords

   Other keywords like func, import, and for serve different purposes, not variable declaration.

3. Final Answer:

   Declares a variable with a name and type -> Option D

4. Quick Check:

   var declares variables [OK]

Hint: Remember: var means variable declaration [OK]

Common Mistakes:

• Confusing var with func or import
• Thinking var creates loops
• Assuming var is for constants

2. Which of the following is the correct way to declare an integer variable named count using var in Go?

easy

A. var count int

B. var count = int

C. count var int

D. int var count

Solution

1. Step 1: Recall Go variable declaration syntax

   In Go, the correct syntax is var variableName type, so var count int is correct.

2. Step 2: Check other options for syntax errors

   Options A, C, and D do not follow Go's syntax rules for variable declaration.

3. Final Answer:

   var count int -> Option A

4. Quick Check:

   var name type = var count int [OK]

Hint: Use 'var name type' format for declaration [OK]

Common Mistakes:

• Placing var after variable name
• Using '=' without value
• Swapping type and var keywords

3. What will be the output of this Go program?

package main
import "fmt"
func main() {
    var x int = 10
    var y int
    y = 5
    fmt.Println(x + y)
}

medium

A. 5

B. 10

C. 15

D. 0

Solution

1. Step 1: Identify variable values

   Variable x is declared with value 10, y is declared then assigned 5.

2. Step 2: Calculate the sum printed

   The program prints x + y which is 10 + 5 = 15.

3. Final Answer:

   15 -> Option C

4. Quick Check:

   10 + 5 = 15 [OK]

Hint: Add assigned values of variables to find output [OK]

Common Mistakes:

• Assuming uninitialized y is zero without assignment
• Confusing variable declaration with initialization
• Ignoring the assignment to y

4. Find the error in this Go code snippet:

package main
func main() {
    var name string = "Go"
    var age
    age = 10
}

medium

A. Missing type for variable 'age' in declaration

B. Cannot assign value after declaration

C. String value assigned to integer variable

D. Variable 'name' declared incorrectly

Solution

1. Step 1: Check variable declarations

   The variable age is declared without a type or initial value, which is invalid in Go.

2. Step 2: Understand Go's requirement for var declarations

   Go requires a type or an initial value when using var. Here, age has neither.

3. Final Answer:

   Missing type for variable 'age' in declaration -> Option A

4. Quick Check:

   var needs type or value [OK]

Hint: Always specify type or initial value with var [OK]

Common Mistakes:

• Declaring var without type or value
• Assuming assignment after declaration fixes type
• Confusing var with := shorthand

5. You want to declare two variables, a as an integer with value 5 and b as a string with value "hello", using var. Which is the correct way to do this in Go?

hard

A. var a, b int = 5, "hello"

B. var a int = 5; var b string = "hello"

C. var a = 5, b = "hello"

D. var a int, b string = "hello", 5

Solution

1. Step 1: Understand type declaration for multiple variables

   In Go, when declaring multiple variables with different types, each must be declared separately or with explicit types.

2. Step 2: Evaluate each option

   var a, b int = 5, "hello" tries to declare both as int but assigns a string to b, which is invalid. var a = 5, b = "hello" uses shorthand but mixes types without explicit declaration. var a int, b string = "hello", 5 mixes types incorrectly in one statement. var a int = 5; var b string = "hello" correctly declares each variable with its type and value.

3. Final Answer:

   var a int = 5; var b string = "hello" -> Option B

4. Quick Check:

   Separate var declarations for different types [OK]

Hint: Declare different types separately with var [OK]

Common Mistakes:

• Trying to declare different types in one var line
• Mixing types without explicit declaration
• Using shorthand := incorrectly with var