linkTransforms

As mentioned before, each line in RxLine is a stream of objects and a transform that is to be applied on those objects. The core of any transform is a function that returns one or more values based on given value either synchronously or asynchronously, i.e.:

1export type Function<I, O> = (i: I) => O | Promise<O> | Observable<O>;

Working with these functions can be inconvenient due to different possible return types. RxLine provides the Transform class and transform() function to address that inconvenience:

1import { transform } from 'rxline';

2import { from } from 'rxjs';

3

4

5const X = transform(async x => await somefunc(x));

6const Y = transform(x => from([x, x + 1]));

7const Z = X.combine(Y);

8Z.apply(42).subscribe(console.log);

9

10// Result:

11// > somefunc(42)

12// > somefunc(42) + 1

.combine() can also be provided a Function directly:

1const Z = transform(async x => await somefunc(x))

2           .combine(x => from([x, x + 1]));

Transforms are the objects that you should provide to a line's .pipe() method. For convenience, if you provide it with any Function, it will automatically wrap it with the transform() method:

1const l = line(...); // --> or files(...) or any other line generator

2

3// These two are equivalent

4l.pipe(x => x + 2);             // --> These two are equivalent

5l.pipe(transform(x => x + 2));  // --> These two are equivalent

Additionally, chaining pipe on a line (or providing multiple arguments to it) is equivalent of calling .combine() on the line's transform:

1const l = line(...);

2

3// These three are equivalent:

4l.pipe(transformA).pipe(transformB).pipe(transformC);       // --> These three are equivalent

5l.pipe(transformA, transformB, transformC);                 // --> These three are equivalent

6l.pipe(transformA.combine(transformB).combine(transformC)); // --> These three are equivalent

Which can be helpful in writing your own custom transforms:

1import { transpile } from 'typescript';

2import { mapExt, mapContent } from 'rxline';

3

4export const compileTS = 

5    transform(mapContent(content => transpile(content)))    // --> so will transpile the typescript

6      .combine(mapExt(() => '.js'));                        // --> and change the extension to `.js`

Transforms