Golang，写入csv文件结果文件有时为空

Question

I'm working on a parsetable and decided I'd like to see the table in a readable format. When I created the csv with a large grammar, it successfully outputs the results. However, the parse table isn't correct. So, I'm trying to test with a more simple grammar. For some reason this code produces a csv file with my large grammar, but with the simple grammar the file is blank. What am I doing wrong here?

func WriteTableToFile() {
    f, err := os.Create("tableFile3.csv")
    Check(err)
    defer f.Close()
    w := csv.NewWriter(f)
    var tsl []string
    tsl = append(tsl, " ")
    tsl, _ = UnionSlices(tsl, TerminalSymbolList)
    w.Write(tsl)
    fmt.Println(tsl)

    for ntk := range ParseTable {
        var writeSlice []string
        writeSlice = append(writeSlice, ntk)
        for _, tk := range TerminalSymbolList {
            for _, p := range ParseTable[ntk][tk] {
                writeSlice = append(writeSlice, p)
                fmt.Println("appending ", p)
            }
        }
        w.Write(writeSlice)
        fmt.Println("wrote ", writeSlice)
    }
}

Answer 1

You need to call the Flush method of your CSV writer to ensure all buffered data is written to your file before closing the file. You can use the following modification:

f, err := os.Create("tableFile3.csv")
Check(err)
w := csv.NewWriter(f)
defer func() {
    w.Flush()
    f.Close()
}()

This concept can be extended to apply to all writers that use buffers.

Oddly enough, the Flush method doesn't return anything, unlike the error returned by the Flush method of a *bufio.Writer but you can use the Error method to check for errors that might have occurred during a preceding Write or Flush call.