Go Structs

The developers who don't like OOP and are yet to figure out the precise difference between a class & object can breath easy now. 

Go has got rid of Classes.

Is Go an Object Oriented Language?

Before you read my version, Find the official answer here. In a strict sense, personally I believe that Go doesn't have the essential attributes to be called an OOP language. Go doesn't have the concept of Object, Inheritance & Polymorphism. Does this make things simple? You may choose to differ but I think, Yes it does. That's one of the various reasons I like Go - it's simple & yet so powerful. 

What are Structs?

Go has structs which are behaviorally similar to classes and can be associated with Methods. Struct is a custom type which represents a real world entity with its properties, and each property may have its own type. 

• Structs are value types.

See the following code sample where a struct named Person has 2 fields (properties) - name of type string and age of type int.

RefCode#1.1

package main

import "fmt"

type Person struct {
 name string
 age  int
}

func main() {
 p := Person{}
 fmt.Println("Default values for Person is: ", p)
}

Output RefCode#1.1

Default values for Person is:  {0}

Play with the above code

As we've not provided any value to the struct fields name and age the output is initialized with default values i.e. empty string or zero; depending on the data type of the fields.

Another sample RefCode#1.2

package main

import "fmt"

type Person struct {
 name string
 age  int
}

func main() {
 p := Person{"Steve", 56} // assign value in the order in which they are defined
 fmt.Println("Person's name & age is: ", p)
}

Output RefCode#1.2

Person's name & age is:  {Steve 56}

Play with the above code

In the following code, we've provided a value that is reflected in the output.
sample RefCode#1.2 can be rewritten as:

Sample RefCode#1.3

package main

import "fmt"

type Person struct {
 name string
 age  int
}

func main() {
 p := Person{age: 56, name: "Steve"} //assign value by variable name and :
 fmt.Println("Person's name & age is: ", p)

 fmt.Println("Person's age is: ", p.age)

}

The output of the above sample:

Person's name & age is:  {Steve 56}
Person's age is:  56

Play with the above code.

If you've observed the above code samples carefully you might have noticed how a struct is initialized. If you're new to programming you can read the following section.

Initialization of a Struct

An instance of type person can be created by any one of the following two ways:

1. var p Person
--- This creates a local person variable with default values set to zero i.e. age = 0 and name = ""  

"" represents empty string

2. p := new(Person)

This allocates default values for the struct fields age and name. It returns a pointer. 

Assigning Values to Struct Fields

Use any of the two ways described below:

1. p := Person{age: 29, name: "Basant"} 

        --- You can change the order of the fields, can also be written as follows:
        p := Person{name: "Basant", age: 29}

2. p := Person{29, "Basant"}

        --- You must know the order of the field and maintain it. 

Accessing Struct Fields

Fields are accessed using the . operator (dot operator).

fmt.Println("Person's age is: ", p.age)

The above line of code is used in  RefCode#1.3.

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