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Get started with Reason

Get started with Reason

We will kick off with the basics and then quickly go into how to leverage features like variant types and pattern matching to make impossible states impossible. After you gained some knowledge about the basics the course will dig even further into ReasonReact.

Nikolaus Graf

April 26, 2018
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  1. type person = { name: string, age: int, }; let

    jane = {name: "Jane", age: 40};
  2. type person = { name: string, age: int, }; let

    jane = {name: "Jane", age: 40}; let tim = {...jane, name: "Tim"};
  3. const pieces = [ { kind: "king", color: "black", position:

    [3, 4] }, { kind: "pawn", color: "black", position: [4, 2] }, { kind: "knight", color: "white", position: [3, 3] } ]; JavaScript
  4. interface Piece { kind: string; color: string; position: number[]; }

    const pieces = [ { kind: "king", color: "black", position: [3, 4] }, { kind: "pawn", color: "black", position: [4, 2] }, { kind: "knight", color: "white", position: [3, 3] } ]; const getKinds = (pieces: Piece[]) => pieces.map(piece => piece.kind); TypeScript
  5. interface Piece { kind: string; color: string; position: number[]; }

    const pieces = [ { kind: "king", color: "black", position: [3, 4] }, { kind: "pawn", color: "black", position: [4, 2] }, { kind: "knight", color: "white", position: [3, 3] } ]; const getKinds = (pieces: Piece[]) => pieces.map(piece => piece.kind); TypeScript
  6. type piece = { kind: string, color: string, position: (int,

    int), }; let pieces = [ {kind: "king", color: "black", position: (3, 4)}, {kind: "pawn", color: "black", position: (4, 2)}, {kind: "knight", color: "white", position: (3, 3)}, ]; let getKinds = pieces => List.map(item => item.kind, pieces); Reason
  7. type direction = | Up | Down | Left |

    Right; let move = Left;
  8. type color = Black | White; type kind = Queen

    | King | Rook | Bishop | Knight | Pawn; type piece = { color, kind, position: (int, int), }; let pieces = [ {kind: King, color: Black, position: (3, 4)}, {kind: Pawn, color: Black, position: (4, 2)}, {kind: Knight, color: White, position: (3, 3)}, ];
  9. type color = Black | White; type kind = Queen

    | King | Rook | Bishop | Knight | Pawn; type piece = { color, kind, position: (int, int), }; let pieces = [ {kind: King, color: Black, position: (3, 4)}, {kind: Pawn, color: Black, position: (4, 2)}, {kind: Knight, color: White, position: (3, 3)}, ];
  10. type color = Black | White; type kind = Queen

    | King | Rook | Bishop | Knight | Pawn; type piece = { color, kind, position: (int, int), }; let pieces = [ {kind: King, color: Black, position: (3, 4)}, {kind: Pawn, color: Black, position: (4, 2)}, {kind: Knight, color: White, position: (3, 3)}, ];
  11. switch (1) { | 0 => "off" | 1 =>

    "on" | _ => "off" };
  12. let displayText = switch (1) { | 0 => "off"

    | 1 => "on" | _ => "off" };
  13. type data = {names: list(string)}; type request = | Loading

    | Error(int) | Success(data); let ui = switch (Loading) { | Loading => "Loading ..." | Error(code) => "Something went wrong. Error: " ++ string_of_int(code) | Success(data) => List.fold_left((a, b) => a ++ b, "Names:", data.names) };
  14. type data = {names: list(string)}; type request = | Loading

    | Error(int) | Success(data); let ui = switch (Loading) { | Loading => "Loading ..." | Error(401) => "You aren’t authenticated." | Error(code) => "Something went wrong. Error: " ++ string_of_int(code) | Success(data) => List.fold_left((a, b) => a ++ b, "Names:", data.names) };
  15. type data = {names: list(string)}; type request = | Loading

    | Error(int) | Success(data); let ui = switch (Loading) { | Loading => "Loading ..." | Error(401 | 402) => "You aren’t authenticated." | Error(code) => "Something went wrong. Error: " ++ string_of_int(code) | Success(data) => List.fold_left((a, b) => a ++ b, "Names:", data.names) };
  16. let foo = None; let foo = Some(42); let foo

    = Some([1, 2, 3]); let foo = Some("Hello World!");
  17. let foo = None; let foo = Some(42); let foo

    = Some([1, 2, 3]); let foo = Some("Hello World!"); switch (foo) { | None => "Sadly I don't know." | Some(value) => "It's " ++ value };
  18. let name = (~firstName, ~lastName) => firstName ++ " "

    ++ lastName; /* Jane Doe */ name(~firstName="Jane", ~lastName="Doe"); /* Jane Doe */ name(~lastName="Doe", ~firstName="Jane");
  19. Stateless Component let component = ReasonReact.statelessComponent("Greeting"); let make = (_children)

    => { ...component, render: _self => <h1>(ReasonReact.string("Hello"))</h1>, }; ReactDOMRe.renderToElementWithId(<Greeting />, "root"); Greeting.re App.re
  20. Props let component = ReasonReact.statelessComponent("Greeting"); let make = (~name, _children)

    => { ...component, render: _self => <h1>(ReasonReact.string(“Hello " ++ name))</h1>, }; ReactDOMRe.renderToElementWithId(<Greeting name="Helsinki" />, "root"); Greeting.re App.re
  21. Props let component = ReasonReact.statelessComponent("Greeting"); let make = (~name, _children)

    => { ...component, render: _self => <h1>(ReasonReact.string("Hello " ++ name))</h1>, }; ReactDOMRe.renderToElementWithId(<Greeting name="Helsinki" />, "root"); Greeting.re App.re
  22. Props let component = ReasonReact.statelessComponent("Greeting"); let make = (~name, _children)

    => { ...component, render: _self => <h1>(ReasonReact.string("Hello " ++ name))</h1>, }; ReactDOMRe.renderToElementWithId(<Greeting name="Helsinki" />, "root"); Greeting.re App.re
  23. type state = {count: int}; type action = | Add(int)

    | Reset; let s = ReasonReact.string;
  24. type state = {count: int}; type action = | Add(int)

    | Reset; let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter");
  25. type state = {count: int}; type action = | Add(int)

    | Reset; let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter"); let make = _children => { ...component, initialState: () => {count: 0},
  26. type state = {count: int}; type action = | Add(int)

    | Reset; let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter"); let make = _children => { ...component, initialState: () => {count: 0}, reducer: (action, state) => switch (action) { | Add(value) => ReasonReact.Update({count: state.count + value}) | Reset => ReasonReact.Update({count: 0}) },
  27. type state = {count: int}; type action = | Add(int)

    | Reset; let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter"); let make = _children => { ...component, initialState: () => {count: 0}, reducer: (action, state) => switch (action) { | Add(value) => ReasonReact.Update({count: state.count + value}) | Reset => ReasonReact.Update({count: 0}) }, render: self => <div> (s(string_of_int(self.state.count)))
  28. let s = ReasonReact.string; let component = ReasonReact.reducerComponent("Counter"); let make

    = _children => { ...component, initialState: () => {count: 0}, reducer: (action, state) => switch (action) { | Add(value) => ReasonReact.Update({count: state.count + value}) | Reset => ReasonReact.Update({count: 0}) }, render: self => <div> (s(string_of_int(self.state.count))) <button onClick=(_event => self.send(Add(1)))> (s(“Add")) </button> <button onClick=(_event => self.send(Add(2)))> (s("Add 2")) </button> <button onClick=(_event => self.send(Reset))> (s("Reset")) </button> </div>, };
  29. [@bs.module "rebass"] external jsArrow : ReasonReact.reactClass = "Arrow"; let make

    = (~direction: string, children) => ReasonReact.wrapJsForReason( ~reactClass=jsArrow, ~props={"direction": direction}, children, );
  30. [@bs.module "rebass"] external jsArrow : ReasonReact.reactClass = "Arrow"; type direction

    = | Up | Down; let make = (~direction, children) => { let directionString = switch (direction) { | Up => "up" | Down => "down" }; ReasonReact.wrapJsForReason( ~reactClass=jsArrow, ~props={"direction": directionString}, children, ); };