Re: Design with appender: good or bad?

[monarch_dodra]

On Thursday, 10 April 2014 at 13:29:39 UTC, Chris wrote:
Thanks. But the question was not about how to print it to 
console, but whether there are any hidden dangers in using 
Appender in this way, like the one Rene mentioned.

AFAIK, no. In fact, arguably, it's saf*er*, since an appender has 
a "true" reference semantic, whereas a slice has "half reference 
semantics": If you modify an *item* all instances will see it, 
but if you *add* some items, only 1 will see it.

But I guess it kind of depends on what you want.

EG:
//----
struct S1
{
  Appender!(string[]) buf;
  string name;

  this(string name) {
    this.name = name;
    buf = appender!(string[]);
  }

  public void addItem (string item) @property
  {
    buf.put(item);
  }

  @property string[] items()
  {
    return buf.data;
  }
}

struct S2
{
  string[] items;
  string name;

  this(string name) {
    this.name = name;
  }

  public void addItem (string item) @property
  {
    items ~= item;
  }
}

void main()
{
    foreach ( S ; TypeTuple!(S1, S2) )
    {
        auto bob = S("Bob");
        bob.addItem("PS4");
        auto bob2 = bob;
        bob2.addItem("XBOXONE");

        writefln("%s.bob  %s", S.stringof, bob.items);
        writefln("%s.bob2 %s", S.stringof, bob2.items);
    }
}
//----
S1.bob  ["PS4", "XBOXONE"]
S1.bob2 ["PS4", "XBOXONE"]
S2.bob  ["PS4"]
S2.bob2 ["PS4", "XBOXONE"]
//----

That said, it feels like you are using Appender like a container. 
Maybe "Array" is a better fit?