The Go Programming Language

6.3 Composing Types by Struct Embedding

Consider the type ColoredPoint:

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gopl.io/ch6/coloredpoint

import "image/color"

type Point struct{ X, Y float64 }

type ColoredPoint struct {
    Point
    Color color.RGBA
}

We could have defined ColoredPoint as a struct of three fields, but instead we embedded a Point to provide the X and Y fields. As we saw in Section 4.4.3, embedding lets us take a syntactic shortcut to defining a ColoredPoint that contains all the fields of Point, plus some more. If we want, we can select the fields of ColoredPoint that were contributed by the embedded Point without mentioning Point:

var cp ColoredPoint
cp.X = 1
fmt.Println(cp.Point.X) // "1"
cp.Point.Y = 2
fmt.Println(cp.Y) // "2"

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