Defining structs in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a struct named Person.

Go

type [1] struct {
    Name string
    Age  int
}

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

AData

Bperson

CStruct

DPerson

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase struct names which are unexported.

Using reserved words like Struct.

The struct name should start with a capital letter to be exported. Here, Person is the correct struct name.

2fill in blank

medium

Complete the code to create a variable of type Person.

Go

var p [1]

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

Astruct

Bint

CPerson

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using basic types like int or string instead of the struct name.

Using the keyword struct directly.

To create a variable of the struct type, use the struct's name Person.

3fill in blank

hard

Fix the error in the struct field definition.

Go

type Car struct {
    Brand [1]
    Year  int
}

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

Astring

Bint

Cstr

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using capitalized types like String.

Using non-existent types like str.

In Go, the correct type for text is string (all lowercase).

4fill in blank

hard

Fill both blanks to define a struct with two fields.

Go

type Book struct {
    Title  [1]
    Pages  [2]
}

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

Astring

Bint

Cfloat64

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using float64 for Pages which should be an integer.

Using bool for text fields.

The Title should be a string and Pages should be an int because pages are whole numbers.

5fill in blank

hard

Fill all three blanks to define a struct and create a variable of that struct.

Go

type [1] struct {
    Name  string
    Age   [2]
}

var p [3]

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

APerson

Bint

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatch between struct name and variable type.

Using string for Age instead of int.

The struct is named Person, Age is an int, and the variable p is of type Person.

Practice

1. What is the purpose of defining a struct in Go?

easy

A. To create a new function

B. To group related data fields into a single unit

C. To declare a package

D. To import external libraries

Solution

1. Step 1: Understand the role of structs

   Structs are used to group related data fields together in one unit, like a blueprint for an object.

2. Step 2: Compare with other options

   Functions, packages, and imports serve different purposes unrelated to grouping data.

3. Final Answer:

   To group related data fields into a single unit -> Option B

4. Quick Check:

   Struct = grouped data [OK]

Hint: Structs bundle related info like a real-world object [OK]

Common Mistakes:

• Confusing structs with functions
• Thinking structs declare packages
• Mixing structs with imports

2. Which of the following is the correct way to define a struct named Person with fields Name (string) and Age (int)?

easy

A. type Person { Name string; Age int }

B. struct Person { Name string; Age int }

C. type Person struct { Name string; Age int }

D. Person struct { Name string; Age int }

Solution

1. Step 1: Recall Go struct syntax

   In Go, structs are defined using the syntax: type Name struct { fields }.

2. Step 2: Check each option

   type Person struct { Name string; Age int } matches the correct syntax. Options A, B, and C miss the 'type' keyword or 'struct' keyword placement.

3. Final Answer:

   type Person struct { Name string; Age int } -> Option C

4. Quick Check:

   Correct struct syntax = type Person struct { Name string; Age int } [OK]

Hint: Remember: 'type Name struct { fields }' [OK]

Common Mistakes:

• Omitting 'type' keyword
• Missing 'struct' keyword
• Incorrect order of keywords

3. What will be the output of the following Go code?

package main
import "fmt"
type Car struct {
  Brand string
  Year  int
}
func main() {
  c := Car{Brand: "Toyota", Year: 2020}
  fmt.Println(c.Brand)
}

medium

A. Car{Brand: "Toyota", Year: 2020}

B. 2020

C. Compilation error

D. Toyota

Solution

1. Step 1: Understand struct initialization

   The struct Car is initialized with Brand="Toyota" and Year=2020.

2. Step 2: Identify printed field

   The code prints c.Brand, which is "Toyota".

3. Final Answer:

   Toyota -> Option D

4. Quick Check:

   Print c.Brand = Toyota [OK]

Hint: Print field with dot: variable.FieldName [OK]

Common Mistakes:

• Printing the whole struct instead of a field
• Confusing field names
• Expecting Year instead of Brand

4. Identify the error in the following Go code snippet:

package main
import "fmt"
type Book struct {
  Title string
  Pages int
}

func main() {
  b := Book{Title: "Go Guide", Pages: "300"}
  fmt.Println(b)
}

medium

A. Pages field has wrong type, should be int not string

B. Missing import for fmt package

C. Struct fields must be lowercase

D. Cannot print struct directly

Solution

1. Step 1: Check field types in struct initialization

   The Pages field is declared as int but assigned a string "300" which is a type mismatch.

2. Step 2: Verify other possible errors

   Import for fmt package is present. Struct fields can be uppercase. Printing structs directly is allowed.

3. Final Answer:

   Pages field has wrong type, should be int not string -> Option A

4. Quick Check:

   Type mismatch in struct field assignment [OK]

Hint: Match field types exactly when initializing structs [OK]

Common Mistakes:

• Assigning string to int field
• Expecting compilation error from printing struct
• Thinking struct fields must be lowercase

5. Given the struct definition:

type Employee struct {
  Name   string
  Salary int
  Active bool
}

Which of the following code snippets correctly creates a slice of Employee structs with only active employees having salary above 50000?

hard

A. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}}
var filtered []Employee
for _, e := range emps {
if e.Active && e.Salary > 50000 {
filtered = append(filtered, e)
}
}

B. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}}
filtered := []Employee{}
for i := range emps {
if emps[i].Salary > 50000 {
filtered = append(filtered, emps[i])
}
}

C. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}}
filtered := []Employee{}
for _, e := range emps {
if e.Active || e.Salary > 50000 {
filtered = append(filtered, e)
}
}

D. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}}
filtered := []Employee{}
for _, e := range emps {
if e.Active && e.Salary < 50000 {
filtered = append(filtered, e)
}
}

Solution

1. Step 1: Understand filtering criteria

   We want only employees who are active and have salary above 50000.

2. Step 2: Check each code snippet logic

   emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}} var filtered []Employee for _, e := range emps { if e.Active && e.Salary > 50000 { filtered = append(filtered, e) } } uses 'e.Active && e.Salary > 50000' which matches criteria. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}} filtered := []Employee{} for i := range emps { if emps[i].Salary > 50000 { filtered = append(filtered, emps[i]) } } misses active check. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}} filtered := []Employee{} for _, e := range emps { if e.Active || e.Salary > 50000 { filtered = append(filtered, e) } } uses '||' which includes inactive employees. emps := []Employee{{"Alice", 60000, true}, {"Bob", 45000, true}, {"Carol", 70000, false}} filtered := []Employee{} for _, e := range emps { if e.Active && e.Salary < 50000 { filtered = append(filtered, e) } } uses salary < 50000 which is wrong.

3. Final Answer:

   The code that filters using e.Active && e.Salary > 50000 -> Option A

4. Quick Check:

   Filter with '&&' for both conditions [OK]

Hint: Use && to combine multiple conditions correctly [OK]

Common Mistakes:

• Using || instead of && for filtering
• Ignoring the Active field in filter
• Using wrong salary comparison operator