cascade ·

Method & assignment cascades for Nim, inspired by Smalltalk & Dart.

cascade is a macro for Nim that implements method cascades, a feature originally from Smalltalk that's made its way into modern languages like Dart and Kotlin.

It allows you to avoid repeating an object's name for each method call or assignment. A common case is something like a button:

# before
var res = Button()
res.text = "ok"
res.width = 30
res.color = "#13a89e"
res.enable()

With cascade, you don't need to repeat yourself:

# after
let btn = cascade Button():
  text = "ok"
  width = 30
  color = "#13a89e"
  enable()

Also notice you can avoid declaring a var if you don't need to modify the target object after the fact — the object is mutable within the cascade block but becomes a let binding outside of that block.

installation & usage

Install using Nimble:

nimble install cascade

Then import and use:

import cascade

let x = cascade y:
  z = 10
  f()

supported constructs

• field assignment

```nim let foo = cascade Foo(): bar = 100

# ↑ equivalent ↓

var foo = Foo() foo.bar = 100 ```

• nested field assignment

```nim let foo = cascade Foo(): bar.baz.qux = "awesome"

# ↑ equivalent ↓

var foo = Foo() foo.bar.baz.qux = "awesome" ```

• proc/template/method calls

```nim let foo = cascade Foo(): fn("hello", "world")

# ↑ equivalent ↓

var foo = Foo() foo.fn("hello", "world") ```

• nested calls on fields

```nim let foo = cascade Foo(): bar.baz.seqOfStrings.add "more awesome"

# ↑ equivalent ↓

var foo = Foo() foo.bar.baz.seqOfStrings.add "more awesome" ```

• if and when conditionals

```nim let foo = cascade Foo(): if someCondition: bar.baz = 2

# ↑ equivalent ↓

var foo = Foo() if someCondition: foo.bar.baz = 2 ```

• cascades can be nested within each other

```nim let foo = cascade Foo(): bar = cascade Bar(): baz = cascade Baz(): str = "we're down here now!"

# ↑ equivalent ↓

var foo = Foo() foo.bar = Bar() foo.bar.baz = Baz(str: "we're down here now!") ```

Is something missing? Check the open issues first or open a new one. Pull requests are appreciated!

building

To build cascade from source you'll need to have Nim installed, and should also have Nimble, Nim's package manager.

1. Clone the repo: git clone https://github.com/haltcase/cascade.git
2. Move into the newly cloned directory: cd cascade
3. Make your changes: cascade.nim, tests/tests.nim
4. Run tests: nimble test

contributing

You can check the issues for anything unresolved, search for a problem you're encountering, or open a new one. Pull requests for improvements are also welcome.

license

MIT © Bo Lingen / haltcase