Re: Switch between two structs with csvreader
On Friday, 6 November 2020 at 19:35:47 UTC, H. S. Teoh wrote:
You can use the typeof() operator to capture the type of a
long, unwieldy type in an alias. This is useful if you ever
need to store such a return type somewhere, e.g.:
alias T = typeof(csvReader(...));
struct MyStorage {
T result;
}
MyStorage s;
s.result = csvReader(...);
Let the compiler figure out the type for you. :-)
T
That's great, thanks!
S
Re: Switch between two structs with csvreader
On Fri, Nov 06, 2020 at 07:17:53PM +, Selim Ozel via Digitalmars-d-learn
wrote:
> On Thursday, 5 November 2020 at 22:36:36 UTC, Anonymouse wrote:
> > If I'm not mistaken the `csvReader` function returns a range struct,
> > and the full type is something long and unwieldy like
> > `CsvReader!(struct_type1, cast(Malformed)1, string, dchar,
> > string[])`. So just think of `records` as being that.
>
> I actually first going this route but couldn't figure out the correct
> name for that data type. It is quite long.
[...]
You can use the typeof() operator to capture the type of a long,
unwieldy type in an alias. This is useful if you ever need to store such
a return type somewhere, e.g.:
alias T = typeof(csvReader(...));
struct MyStorage {
T result;
}
MyStorage s;
s.result = csvReader(...);
Let the compiler figure out the type for you. :-)
T
--
Guns don't kill people. Bullets do.
Re: Switch between two structs with csvreader
On Thursday, 5 November 2020 at 22:36:36 UTC, Anonymouse wrote: If I'm not mistaken the `csvReader` function returns a range struct, and the full type is something long and unwieldy like `CsvReader!(struct_type1, cast(Malformed)1, string, dchar, string[])`. So just think of `records` as being that. I actually first going this route but couldn't figure out the correct name for that data type. It is quite long. You need two different variables and two different `foreach`es. For the same code to work on both types, the easy solution is templates. Perhaps make the `foreach` part after the reads a templated function that accepts any type passed to it? Embedding the foreach loop inside a template function and deciding on the data type at the higher level function solved my issue. Thanks for the pointer! Best, Selim
Re: Switch between two structs with csvreader
On Thursday, 5 November 2020 at 21:18:52 UTC, Selim Ozel wrote:
auto records = rawtext.csvReader!struct_type1(';');
D is statically typed and `auto` means "deduce this type for me
based on this one function's return value". It is not like
JavaScript's `var` whose type may change.
If I'm not mistaken the `csvReader` function returns a range
struct, and the full type is something long and unwieldy like
`CsvReader!(struct_type1, cast(Malformed)1, string, dchar,
string[])`. So just think of `records` as being that.
(You can tell what type it is at compilation with `pragma(msg,
typeof(records).stringof)`.)
if(aControlCondition) {
records = rawtext.csvReader!struct_type2(';');
Here `csvReader!struct_type2(';')` returns a value of type
`CsvReader!(struct_type2, ...)`, which is a different type from
that of `records` (and they're not implicitly convertible). So
the error message is right. If `auto` worked like `var` your code
would work, but it doesn't.
You need two different variables and two different `foreach`es.
For the same code to work on both types, the easy solution is
templates. Perhaps make the `foreach` part after the reads a
templated function that accepts any type passed to it?
Switch between two structs with csvreader
Hi There,
I am trying to switch between two structs as I am using the
csvReader on a raw string. The pseudo-code below throws a "cannot
implicitly convert" error due to difference between struct_type1
and struct_type2. I must be doing something wrong or have a wrong
understanding of how this function works. Could someone give a
good suggestion on handling this?
Thanks!
Best,
Selim
auto records = rawtext.csvReader!struct_type1(';');
if(aControlCondition) {
records = rawtext.csvReader!struct_type2(';');
}
// Iterate through each data row.
foreach (record; records) {
writeln(record);
}
