Re: struct, ref in, and UFCS

[Puming via Digitalmars-d-learn]

On Tuesday, 1 July 2014 at 05:26:47 UTC, Ali Çehreli wrote:
On 06/30/2014 10:11 PM, Puming wrote:
> On Tuesday, 1 July 2014 at 05:09:49 UTC, Puming wrote:
>> Hi,
>>
>> I have a struct and want to extends its methods, like:
>>
>> ```d
>> struct Server
>> {
>>   string name;
>>   string ip;
>>   int port;
>>   string user;
>> }
>> ```
>>
>> extension method here:
>>
>> ```d
>> string prompt(ref in Server server)
>> {
>>    return server.user ~ "@" ~ server.ip ~ ":" ~ server.port;
>> }
>>
>> ```
> should be `server.port.to!int`;

I think it should actually be server.port.to!string;

>> is this the correct way to use struct and UFCS? it does not
seem to
>> copy there.

I don't understand your question but I wanted to help others by 
making complete code from your messages:

import std.conv;

struct Server
{
    string name;
    string ip;
    int port;
    string user;
}

string prompt(ref in Server server)
{
    return server.user ~ "@" ~ server.ip ~ ":" ~ 
server.port.to!string;
}

void main()
{
    auto server = Server("bzzt", "192.168.0.1", 80, "nobody");
    string p = server.prompt;
}

Ali

Thanks, This code works and my question is that is this a good 
practice to use `ref in` with structs instead of traditional 
pointer syntax (which does not play well with UFCS though) ? Is 
there any perfomance implications with `ref in`? I tried that it 
does not seem to copy the parameter value, which is good for me:


```d
#!/usr/bin/rdmd

import std.stdio;

struct Server
{
        string name;
}

string prompt(ref in Server server)
{
        __server.name = "new name";
        return server.name ~ ">";
}

Server __server;

void main()
{
        __server.name = "old_name";

        writeln(__server.prompt);
}
```

which prints

```
newname>
```

meaning the `return server.name ~ ">"` code in promt is using a 
reference of __server instead of copying the value.