在Go中读取CSV文件

Question

I'm learning Go. Here is a code snippet that reads CSV file:

func parseLocation(file string) (map[string]Point, error) {
    f, err := os.Open(file)
    defer f.Close()
    if err != nil {
        return nil, err
    }
    lines, err := csv.NewReader(f).ReadAll()
    if err != nil {
        return nil, err
    }
    locations := make(map[string]Point)
    for _, line := range lines {
        name := line[0]
        lat, laterr := strconv.ParseFloat(line[1], 64)
        if laterr != nil {
            return nil, laterr
        }
        lon, lonerr := strconv.ParseFloat(line[2], 64)
        if lonerr != nil {
            return nil, lonerr
        }
        locations[name] = Point{lat, lon}
    }
    return locations, nil
}

Is there a way to improve readability of this code? if and nil noise.

Answer 1

Go is a very verbose language, however you could use something like this:

// predeclare err
func parseLocation(file string) (locations map[string]*Point, err error) {
    f, err := os.Open(file)
    if err != nil {
        return nil, err
    }
    defer f.Close() // this needs to be after the err check

    lines, err := csv.NewReader(f).ReadAll()
    if err != nil {
        return nil, err
    }

    //already defined in declaration, no need for :=
    locations = make(map[string]*Point, len(lines))
    var lat, lon float64 //predeclare lat, lon
    for _, line := range lines {
        // shorter, cleaner and since we already have lat and err declared, we can do this.
        if lat, err = strconv.ParseFloat(line[1], 64); err != nil {
            return nil, err
        }
        if lon, err = strconv.ParseFloat(line[2], 64); err != nil {
            return nil, err
        }
        locations[line[0]] = &Point{lat, lon}
    }
    return locations, nil
}

//edit

A more efficient and proper version was posted by @Dustin in the comments, I'm adding it here for completeness sake:

func parseLocation(file string) (map[string]*Point, error) {
    f, err := os.Open(file)
    if err != nil {
        return nil, err
    }
    defer f.Close()

    csvr := csv.NewReader(f)

    locations := map[string]*Point{}
    for {
        row, err := csvr.Read()
        if err != nil {
            if err == io.EOF {
                err = nil
            }
            return locations, err
        }

        p := &Point{}
        if p.lat, err = strconv.ParseFloat(row[1], 64); err != nil {
            return nil, err
        }
        if p.lon, err = strconv.ParseFloat(row[2], 64); err != nil {
            return nil, err
        }
        locations[row[0]] = p
    }
}

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