Creating struct values in Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a struct value with default zero values.

Go

type Person struct {
    Name string
    Age  int
}

func main() {
    p := [1]{}
    fmt.Println(p)
}

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

Aperson

BPerson

Cstruct

Dnew

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'person' instead of 'Person'.

Using 'new' keyword which returns a pointer, not a value.

To create a struct value, use the struct type name followed by curly braces.

2fill in blank

medium

Complete the code to create a struct value with field values.

Go

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{
        Name: [1],
        Age:  30,
    }
    fmt.Println(p)
}

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

AName

BAlice

C'Alice'

D"Alice"

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted string which causes a compile error.

Using single quotes which are for rune literals.

String values must be enclosed in double quotes in Go.

3fill in blank

hard

Fix the error in creating a struct value with field names.

Go

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{
        [1]: "Bob",
        Age:  25,
    }
    fmt.Println(p)
}

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

Aname

BAGE

CName

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase field names which do not match struct fields.

Using all uppercase which is incorrect.

Field names are case-sensitive and must match exactly as declared in the struct.

4fill in blank

hard

Fill both blanks to create a struct value with fields and print the Name.

Go

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{
        [1]: "Carol",
        [2]: 40,
    }
    fmt.Println(p.Name)
}

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

AName

BAge

Cname

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase field names causing errors.

Mixing up field names.

Use exact field names with correct capitalization to assign values.

5fill in blank

hard

Fill all three blanks to create a struct value, update Age, and print the updated struct.

Go

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{
        [1]: "Dave",
        [2]: 28,
    }
    p.[3] = 29
    fmt.Println(p)
}

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

AName

BAge

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase field names.

Forgetting to update the Age field correctly.

Assign values using exact field names and update the Age field before printing.

Practice

1. What is the correct way to create a struct value with fields Name as "Alice" and Age as 30 in Go?

easy

A. person := Person("Alice", 30)

B. person := Person{30, "Alice"}

C. person := Person{Name: "Alice", Age: 30}

D. person := Person{Name = "Alice", Age = 30}

Solution

1. Step 1: Understand struct literal syntax

   In Go, struct values are created using the syntax StructType{FieldName: value, ...} for clarity and correctness.

2. Step 2: Match the syntax with the given options

   person := Person{Name: "Alice", Age: 30} uses the correct syntax with field names and values. Options A and C use positional values without field names, which is allowed but less clear and can cause errors if order changes. person := Person{Name = "Alice", Age = 30} uses '=' which is invalid in struct literals.

3. Final Answer:

   person := Person{Name: "Alice", Age: 30} -> Option C

4. Quick Check:

   Use field names with colons in struct literals = B [OK]

Hint: Use field names with colons to create structs clearly [OK]

Common Mistakes:

• Using parentheses instead of braces
• Using '=' instead of ':' in struct literals
• Mixing field order without names causing confusion

2. Which of the following is the correct syntax to create a struct value with zero values for all fields in Go?

easy

A. p := Person{}

B. p := Person()

C. p := new(Person)

D. p := Person(nil)

Solution

1. Step 1: Recall zero value struct creation

   In Go, creating a struct with zero values for all fields is done by using empty braces after the struct type: StructType{}.

2. Step 2: Evaluate options

   p := Person{} uses Person{} which creates a struct with zero values. p := Person() uses parentheses which is invalid syntax. p := new(Person) uses new(Person) which returns a pointer, not a struct value. p := Person(nil) uses nil which is invalid for struct values.

3. Final Answer:

   p := Person{} -> Option A

4. Quick Check:

   Empty braces create zero-value struct = C [OK]

Hint: Use empty braces {} to create zero-value struct [OK]

Common Mistakes:

• Using parentheses instead of braces
• Confusing new() pointer with struct value
• Passing nil to struct literal

3. Given the struct and code below, what will be printed?

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{Name: "Bob", Age: 25}
    p.Age = 26
    fmt.Println(p)
}

medium

A. {Bob 25}

B. {Bob 26}

C. Person{Name: "Bob", Age: 26}

D. Syntax error

Solution

1. Step 1: Create struct and modify field

   The struct Person is created with Name "Bob" and Age 25. Then the Age field is updated to 26.

2. Step 2: Print the struct value

   Printing the struct with fmt.Println shows the field values in braces. Since Age was updated to 26, the output is {Bob 26}.

3. Final Answer:

   {Bob 26} -> Option B

4. Quick Check:

   Updated field value shows in output = D [OK]

Hint: Changing a field after creation updates printed struct [OK]

Common Mistakes:

• Assuming original Age remains unchanged
• Expecting struct type name in print output
• Confusing syntax error with valid code

4. What is wrong with the following code snippet?

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{Name: "Eve", Age: "30"}
    fmt.Println(p)
}

medium

A. Age field has wrong type value

B. Missing parentheses in struct creation

C. Name field is not initialized

D. fmt.Println cannot print structs

Solution

1. Step 1: Check field types in struct literal

   The struct Person has Age as int type, but the code assigns "30" which is a string, causing a type mismatch error.

2. Step 2: Identify the error cause

   Assigning a string to an int field is invalid in Go and causes a compile-time error.

3. Final Answer:

   Age field has wrong type value -> Option A

4. Quick Check:

   Field types must match exactly = A [OK]

Hint: Match field types exactly when creating struct values [OK]

Common Mistakes:

• Assigning string to int field
• Confusing struct literal syntax errors
• Thinking fmt.Println can't print structs

5. How can you create a slice of struct values representing three people with names "Anna", "Ben", "Cara" and ages 22, 28, 31 respectively in Go?

hard

A. people := []Person{Person("Anna", 22), Person("Ben", 28), Person("Cara", 31)}

B. people := [Person]{Name: "Anna", Age: 22, Name: "Ben", Age: 28, Name: "Cara", Age: 31}

C. people := []Person{Name: "Anna", Age: 22, Name: "Ben", Age: 28, Name: "Cara", Age: 31}

D. people := []Person{{Name: "Anna", Age: 22}, {Name: "Ben", Age: 28}, {Name: "Cara", Age: 31}}

Solution

1. Step 1: Understand slice of structs syntax

   A slice of structs is created using []StructType{...} with each element as a struct literal.

2. Step 2: Check each option for correct syntax

   people := []Person{{Name: "Anna", Age: 22}, {Name: "Ben", Age: 28}, {Name: "Cara", Age: 31}} correctly creates a slice with three struct literals using field names. people := [Person]{Name: "Anna", Age: 22, Name: "Ben", Age: 28, Name: "Cara", Age: 31} uses array syntax but incorrect literal format. people := []Person{Name: "Anna", Age: 22, Name: "Ben", Age: 28, Name: "Cara", Age: 31} tries to create slice but misses braces for each struct. people := []Person{Person("Anna", 22), Person("Ben", 28), Person("Cara", 31)} uses parentheses which is invalid for struct literals.

3. Final Answer:

   people := []Person{{Name: "Anna", Age: 22}, {Name: "Ben", Age: 28}, {Name: "Cara", Age: 31}} -> Option D

4. Quick Check:

   Slice of structs uses []Type{{...}, {...}} = A [OK]

Hint: Use double braces for slice of struct literals [OK]

Common Mistakes:

• Using parentheses instead of braces for structs
• Missing braces around each struct in slice
• Confusing array and slice syntax