Accessing struct variable outside of {{range .}} scope in golang html template
Question
<!DOCTYPE html>
<html>
<head>
<title> Test </title>
</head>
<body>
<div>
<h2>Reply</h2>
<form action="/post/{{$threadID}}" method="POST">
<input type="text" name="subject" />
<input type="text" name="name" value="Anonymous" />
<input type="text" name="message" />
<input type="submit" value="submit" />
</form>
</div>
<div>
{{range .}}
{{$threadID := .ThreadID}}
<h3>{{.Subject}}</h3>
<h3>{{.Name}}</h3>
<div>{{.DatePosted}}</div>
<div><p>{{.Text}}</p></div>
<br /><br />
{{end}}
</div>
</body>
I have this template, there is a form at the top of the page that requires the threadID from ANY one of the Posts sent (they're all the same, a slice of all posts with a certain threadID), this obviously doesn't work, my only other idea was something along the lines of
{{range .}}
{{if $threadID == nil}}
$threadID := .ThreadID
//build the form same as above
{{end}}
<h3>{{.Subject}}</h3>
<h3>{{.Name}}</h3>
<div>{{.DatePosted}}</div>
<div><p>{{.Text}}</p></div>
<br /><br />
{{end}}
Here is the Post structure and methods if any of the above is unclear.
type Post struct {
threadID int
subject string
name string
text string
date_posted string
}
func (p *Post) ThreadID() int { return p.threadID }
func (p *Post) Subject() string { return p.subject }
func (p *Post) Name() string { return p.name }
func (p *Post) Text() string { return p.text }
func (p *Post) DatePosted() string { return p.date_posted }
And the origin of the slice of posts sent to the template
threadID := r.URL.Path[len("/reply/"):]
replies, err := i.db.Query("SELECT * FROM latest_threads where thread_id="+threadID);
2 answers
solution1
5 2014-03-13 00:41:54
If the Thread Id can only be retrieved from the Post type itself, consider turning your slice of posts into a separate type. Give it a ThreadID method, which simply returns the id for the first post it contains, or zero if none exist.
type PostList []*Post
func (p PostList) ThreadId() int {
if len(p) == 0 {
return 0
}
return p[0].ThreadId
}
Pass this list into the template. Now you can reference it from the template, anywhere outside of the {{range .}} clause.
<form action="/post/{{.ThreadID}}" method="POST">
Exploit warning
As a side note, Little Bobby Tables has an issue with the SQL query. It's possible you are just posting it as a quick example. If not, be advised that your code is a recipe for SQL injection exploits . If the thread ID is numeric, then ensure you parse it as such, before passing it into the SQL query. Eg: Sanitize your inputs.
solution2
3 ACCPTED 2014-03-13 01:38:32
You can pass it all as one struct like so:
layoutData := struct {
ThreadID int
Posts []Post
} {
ThreadID: threadID,
Posts: Posts,
}
Then something like this will work
<!DOCTYPE html>
<html>
<head>
<title> Test </title>
</head>
<body>
<div>
<h2>Reply</h2>
<form action="/post/{{ .ThreadID }}" method="POST">
<input type="text" name="subject" />
<input type="text" name="name" value="Anonymous" />
<input type="text" name="message" />
<input type="submit" value="submit" />
</form>
</div>
<div>
{{range $post := .Posts}}
<h3>{{ $post.Subject}}</h3>
<h3>{{$post.Name}}</h3>
<div>{{$post.DatePosted}}</div>
<div><p>{{$post.Text}}</p></div>
<br /><br />
{{end}}
</div>
</body>
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