golang - Content of a pointer in a slice changes during recursive function run

Question

func getAllCertainDivs(className string, idName string, htmlTag *HtmlTag, matchingDivs *[]*HtmlTag) {
    fmt.Println(htmlTag.Class)
    if htmlTag.XMLName.Local == \"di         


        

Answer 1

The tag variable is declared once at the start of the loop, and the value of tag is overwritten on each iteration. This is the same problem you see in the FAQ with: "What happens with closures running as goroutines?"

You can declare a new variable during each iteration to get a unique pointer for the function call:

for _, tag := range htmlTag.ChildTags {
    tag := tag
    getAllCertainDivs(className, idName, &tag, matchingDivs)
}

Alternatively you can elide the range value, and use the index directly:

for i := range htmlTag.ChildTags {
    getAllCertainDivs(className, idName, &htmlTag.ChildTags[i], matchingDivs)
}