问题
I recently started looking for functional go examples and I found this function:
mapper := func (i interface{}) interface{} {
return strings.ToUpper(i.(string))
}
Map(mapper, New(“milu”, “rantanplan”))
//[“MILU”, “RANTANPLAN”]
Now in this function, as you can see the return value of mapper is:
strings.ToUpper(i.(string)).
But, what does this i.(string) syntax mean? I tried searching, but didn't find anything particularly useful.
回答1:
i.(string) casts (or attempts at least) i (type interface{}) to type string. I say attempts because say i is an int instead, this will panic. If that doesn't sound great to you, then you could change the syntax to
x, ok := i.(string)
In this case if i is not a string, then ok will be false and the code won't panic.
回答2:
i.(string) means converting i(interface{} type) to string type.
来源：https://stackoverflow.com/questions/53577949/what-does-i-string-actually-mean-in-golang-syntax