相同的算法，Go中有多个输入和输出类型的可能性？

Question

I'm currently using draw2d lib to render some image. I noticed the core algorithm and method are the same for building SVG, or PNG images.

I do need to render this images as SVG (for web use) and PNG (for PDF use)

The only difference is at the entry type and output.

for PNG rendering I've

as input:

var gc *draw2dimg.GraphicContext
var img *image.RGBA

img = image.NewRGBA(image.Rect(0, 0, xSize, ySize))
gc = draw2dimg.NewGraphicContext(img)

as output:

draw2dimg.SaveToPngFile(FileName, img)

and for SVG I've:

as input:

var gc *draw2dsvg.GraphicContext
var img *draw2dsvg.Svg

img = draw2dsvg.NewSvg()
gc = draw2dsvg.NewGraphicContext(img)

as output:

draw2dsvg.SaveToSvgFile(FileName, img)

between input and output I've the same implementation.

Is there any way in Go to use different input type and get the same implementation without have to duplicate some code?

Answer 1

As I mentioned in the comment, try to refactor your code by moving the core algorithm part into a function or may be to a different package. To illustrate the idea, bellow is the refactored version of example in https://github.com/llgcode/draw2d README.

package main

import (
    "image"
    "image/color"

    "github.com/llgcode/draw2d"
    "github.com/llgcode/draw2d/draw2dimg"
    "github.com/llgcode/draw2d/draw2dpdf"
    "github.com/llgcode/draw2d/draw2dsvg"
)

func coreDraw(gc draw2d.GraphicContext) {
    // Set some properties
    gc.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
    gc.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
    gc.SetLineWidth(5)

    // Draw a closed shape
    gc.BeginPath()    // Initialize a new path
    gc.MoveTo(10, 10) // Move to a position to start the new path
    gc.LineTo(100, 50)
    gc.QuadCurveTo(100, 10, 10, 10)
    gc.Close()
    gc.FillStroke()
}

func main() {
    format := "svg"

    switch format {
    case "png":
        dest := image.NewRGBA(image.Rect(0, 0, 297, 210.0))
        gc := draw2dimg.NewGraphicContext(dest)
        coreDraw(gc)
        draw2dimg.SaveToPngFile("hello.png", dest)
    case "pdf":
        dest := draw2dpdf.NewPdf("L", "mm", "A4")
        gc := draw2dpdf.NewGraphicContext(dest)
        coreDraw(gc)
        draw2dpdf.SaveToPdfFile("hello.pdf", dest)
    case "svg":
        img := draw2dsvg.NewSvg()
        gc := draw2dsvg.NewGraphicContext(img)
        coreDraw(gc)
        draw2dsvg.SaveToSvgFile("hello.svg", img)
    }
}