<p>(newcomer here)</p>
<p>I'm writing a web server and I'm wondering if there's a better way of doing validation than to repeat code.</p>
<pre><code>func handler1(w http.ResponseWriter, r *http.Request) {
foo, err := GetParam(r, "foo")
if err != nil {
http.NotFound(w, r)
return
}
bar, err := GetParam(r, "bar")
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
restOfCode(foo, bar)
}
func handler2(w http.ResponseWriter, r *http.Request) {
bar, err := GetParam(r, "bar")
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
otherCode(bar)
}
</code></pre>
<p>What are my alternatives? Any ideas? In an ideal world it would be great to have</p>
<pre><code>func handler1(w http.ResponseWriter, r *http.Request) {
foo, bar := tryParam("foo", w, r), tryParam("bar", w, r)
restOfCode(foo, bar)
}
func handler2(w http.ResponseWriter, r *http.Request) {
bar := tryParam("bar", w, r)
otherCode(bar)
}
</code></pre>
<p>(edit: formatting)</p>
<hr/>**评论：**<br/><br/>xtrmity: <pre><p>Make a variadic function that fetches the params, handles any errors and returns the resulting list if there were no errors.</p>
<pre><code>const (
NotFound = iota
BadReq
)
func GetParams(w http.ResponseWriter, r *http.Request, errHandle int, names ...string) []string {
var m = make([]string, 0, len(names))
for _, name := range names {
if param, err := GetParam(r, name); err != nil {
switch errHandle {
case NotFound:
http.NotFound(w, r)
case BadReq:
http.Error(w, err.Error(), http.StatusBadRequest)
}
return nil
} else {
m = append(m, param)
}
}
return m
}
</code></pre>
<p>Use it like this:</p>
<pre><code>func handler1(w http.ResponseWriter, r *http.Request) {
if params := GetParams(w, r, NotFound, "foo", "bar"); params != nil {
restOfCode(params...)
}
}
func handler2(w http.ResponseWriter, r *http.Request) {
if params := GetParams(w, r, BadReq, "bar"); params != nil {
otherCode(params...)
}
}
```
</code></pre>
<p>If you don't want to make <code>restOfCode</code> and <code>otherCode</code> variadic, then just pass the individual indexes from the <code>params</code> result.</p></pre>duncanfoo: <pre><p>Make a table of the expected parameters and check the table and error out.</p>
<pre><code>if !checkParams([]string {"foo", "bar'}) {
http.NotFound(w, r)
return
}
</code></pre></pre>brianolson: <pre><p>Use a middleware approach of making a barHandler that does the "bar" part and then calls the sub handlers for foo or other code.</p></pre>brianolson: <pre><p>extend Go language to accept macros. Call barStuff() macro inside handler1 and handler2</p></pre>
