On Saturday, 14 October 2017 at 03:47:29 UTC, Jonathan M Davis
wrote:
The function to use for conversions in general is std.conv.to.
And really, there isn't much of a reason to ever call toString.
Functions like writeln, format, and to may use it internally,
but it's more or less an anti-pattern to do so in your own code
- especially if we're talking about generic code. If you're
looking to convert something to string, to!string works with
pretty much everything and toString works with considerably
less. And if there's a generic way to convert from string to
something else, it's also with to - e.g. to!int("42"). However,
for that conversion to work, it either has to be a built-in
type so that to understands it, or the type will need a
constructor that takes a string. In general, in order to
generically convert to a user-defined type, either that target
type must have a constructor that accepts that source type, or
the source type must define opCast or an alias to convert to
the target type. std.conv.to is very powerful, but it does need
to have something to work with. If anything approaching a
standard conversion exists, it can be done with std.conv.to;
otherwise, it's going to depend on the type.
I think that in general, you're going to find that converting
to a string works with most everything, but aside from built-in
types, converting from a string with std.conv.to is unlikely to
work. _Some_ types do have constructors that take strings, but
most don't. Built-in types will work, because std.conv.to
understands how to do that conversion. For user-defined types,
either you're likely going to have to parse the string
yourself, or they may contain another function for doing the
conversion (for instance std.datetime.systime.SysTime uses
toISOExtString and fromISOExtString to convert to and from the
ISO extended format for a date and time and has other functions
for other time formats).
This is not what I asked about.
You can also check out std.conv.parse, which acts similarly to
std.conv.to, but whereas to converts the entire string, parse
converts the first portion of a string and therefore is meant
to allow for parsing multiple values from a string.
This is what I asked about. Thanks.
