如何将映射中的值与一组已知值进行比较

Question

I have some code that pulls out the URL parameters from a URL and places it into a map. I can successfully print out the values of the map items that I want to examine.

values := r.URL.Query()

a := values["a"]

fmt.Println(a)

I notice when the values print they print with "[]" surrounding them.

I'd like to value the value of each a,b,c and check to see if it is contained in a comma-delimited string.

allowedA = "value1,value2,value3"

i.e. something similar to:

if(contains(allowedA,a)

Meaning "if the value in 'a' is contained in the variable 'allowedA' then return true.

Any suggestions?

Answer 1

I notice when the values print they print with "[]" surrounding them.

That's because url.Values is map[string][]string, not map[string]string. Use url.Values.Get to access the parameter directly.

I'd like to value the value of each a,b,c and check to see if it is contained in a comma-delimited string.

I'd suggest splitting the string and using the result as map keys, so that you could use the map as a set. I.e.

allowedAMap := map[string]struct{}{}
allowedAStrs := strings.Split(allowedA, ",")
for _, s := range allowedAStrs {
    allowedAMap[s] = struct{}{}
}
//...
if _, ok := allowedAMap[a]; !ok {
    fmt.Println("wrong a")
    return
}
fmt.Println("correct a")