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Merge PR #174 from nblockchain/wip/fp
Start using FP patterns in TypeScript. TODO: move FP helpers to npmjs package?
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| interface IOption { | ||
| /** | ||
| * @deprecated it is better to use `if (foo instanceof None)` so that you can access the .value in the `else` case | ||
| **/ | ||
| IsNone(): boolean; | ||
| /** | ||
| * @deprecated it is better to use `if (!(foo instanceof None))` so that you can access the .value inside the `if` block | ||
| **/ | ||
| IsSome(): boolean; | ||
| } | ||
|
|
||
| export class None { | ||
| public IsNone(): boolean { | ||
| return true; | ||
| } | ||
| public IsSome(): boolean { | ||
| return false; | ||
| } | ||
|
|
||
| /** | ||
| * @deprecated it is better to use `OptionStatic.None` | ||
| **/ | ||
| constructor() {} | ||
| } | ||
| export class Some<T> { | ||
| value: T; | ||
|
|
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| constructor(val: NonNullable<T>) { | ||
| this.value = val; | ||
| } | ||
|
|
||
| public IsNone(): boolean { | ||
| return false; | ||
| } | ||
| public IsSome(): boolean { | ||
| return true; | ||
| } | ||
| } | ||
|
|
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| export type Option<T> = (None | Some<NonNullable<T>>) & IOption; | ||
|
|
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| export class OptionStatic { | ||
| public static None = new None(); | ||
| public static OfObj<T>(obj: T | null | undefined): Option<NonNullable<T>> { | ||
| if (obj === null || obj === undefined) { | ||
| return OptionStatic.None; | ||
| } else { | ||
| return new Some(obj); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| export class TypeHelpers { | ||
| public static IsNullOrUndefined(variable: any) { | ||
| return variable === null || variable === undefined; | ||
| } | ||
|
|
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| // because instanceof doesn't work with primitive types (e.g. String), taken from https://stackoverflow.com/a/58184883/544947 | ||
| public static IsInstanceOf(variable: any, type: any) { | ||
| if (TypeHelpers.IsNullOrUndefined(variable)) { | ||
| throw new Error( | ||
| "Invalid 'variable' parameter passed in: null or undefined" | ||
| ); | ||
| } | ||
| if (TypeHelpers.IsNullOrUndefined(type)) { | ||
| throw new Error( | ||
| "Invalid 'type' parameter passed in: null or undefined" | ||
| ); | ||
| } | ||
|
|
||
| let res: boolean = false; | ||
| if (typeof type == "string") { | ||
| res = typeof variable == type.toLowerCase(); | ||
| } else { | ||
| res = variable.constructor == type; | ||
| } | ||
| return res; | ||
| } | ||
| } |
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