执行：类型[] string没有字段或方法len

Question

I am trying to compile the following function:

func (self algo_t) chk_args(args []string) {
    if args.len() != self.num_args {
        fmt.Fprintf(
            os.Stdout,
            "%s expected %d argument(s), received %d
",
            self.name,
            self.num_args,
            args.len(),
        )
        fmt.Printf("quickcrypt %s
", self.usage)
    }
}

I am receiving the error, args.len undefined (type []string has no field or method len).

Args is of type []string, and the language specification says this is a slice type. The builtin package documentation says v.len() is defined for Slice types. What is going on?

Answer 1

Try using:

func (self *algo_t) chk_args(args []string) {
    if len(args) != self.num_args {
        fmt.Fprintf(
            os.Stdout,
            "%s expected %d argument(s), received %d
",
            self.name,
            self.num_args,
            len(args),
        )
        fmt.Printf("quickcrypt %s
", self.usage)
    }
}

func len(v Type) int is a built in function that allows you to pass in a variable, not a built in function on a type.

As a side note, you probably want chk_args to be a function on a pointer to algo_t like I have in the example.