Go Struct Fields

Introduction

Suppose we have 

type Circle struct { 
    x float64 
    y float64 
    r float64 
}

We can access fields using the . operator: 

fmt.Println(c.x, c.y, c.r) 
c.x = 10 
c.y = 5

The following function circleArea function uses a Circle: 

func circleArea(c Circle) float64 { 
    return math.Pi * c.r*c.r 
}

In main, we have: 

c  := Circle{0, 0, 5} 
fmt.Println(circleArea(c))

Arguments are always copied in Go.

To modify one of the fields inside of the circleArea function, it would not modify the original variable.

Typically we write the function using a pointer to the Circle: 

func circleArea(c *Circle) float64 { 
    return math.Pi * c.r*c.r 
}

And change main to use & before c: 

c  := Circle{0, 0, 5} 
fmt.Println(circleArea(&c))



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