Interop Miscellaneous
Composing bs
Attributes
As you might have guessed, most bs.*
attributes can be used together. Here's an extreme example:
Note that bs.splice
was renamed to bs.variadic
after version 4.08
RE[@bs.val] [@bs.scope "global"] [@bs.variadic]
external draw : ([@bs.as "dog"] _, array(int)) => unit = "draw";
draw([|1, 2|]);
Output:
JSglobal.draw("dog", 1, 2);
Safe External Data Handling
In some cases, the data could either come from JS or BS; it's very hard to give precise type information because of this. For example, for an external promise whose creation could come from the JS API, its failed value caused by Promise.reject
could be of any shape.
BuckleScript provides a solution, bs.open
, to filter out OCaml structured exception data from the mixed data source. It preserves type safety while allowing you to deal with mixed source. It makes use of OCaml’s extensible variant, so that users can mix values of type exn
with JS data.
RElet handleData = [@bs.open] (
fun
| Invalid_argument(_) => 0
| Not_found => 1
| Sys_error(_) => 2
);
/* handleData is 'a => option(int) */
For any input source, as long as it matches the exception pattern (nested pattern match supported), the matched value is returned, otherwise return None
.