Creating a WIT Specification for the split-str Example
Before we do any coding, let’s first define our interface. WIT is an Interface Definition Language (IDL) used to describe Wasm modules. It is provided in files with the .wit extension.
In this example, we’ll work with strings and nested types. Let’s create a function that takes a string, splits it at every occurrence of a delimiting string, and then returns each sub-string along with its starting indices. The output will be sent back as a list of records (aka structures).
To start, let’s create a new work directory, and inside of it we’ll make a new file called split.wit. The WIT IDL we need is below, so we can go ahead and paste that in and save it.
record subphrase {
str: string,
idx: s32
}
split-str: func(phrase: string, delim: string) -> list<subphrase>
Now we’re ready to write some code.