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drothmaler/readonly.ts

Last active May 6, 2020 07:26
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Revisions

  1. drothmaler revised this gist May 6, 2020. 1 changed file with 24 additions and 8 deletions.
    32 changes: 24 additions & 8 deletions readonly.ts
    View file
    Original file line number Diff line number Diff line change
    @@ -1,4 +1,3 @@

    interface Foo {
    n: number
    s: string
    @@ -8,11 +7,13 @@ class Bar1 {
    n: number
    s: string
    foo: Foo
    }
    } // anything can be changed

    let bar1 = new Bar1()

    bar1.n = 42 // <-- Working
    bar1.s = "foo" // <-- Working
    bar1.s.length = 0 // <-- Error (string is always immutable)
    bar1.foo = { // <-- Working
    n: 21,
    s: "bar"
    @@ -24,28 +25,31 @@ class Bar2 {
    readonly n: number
    readonly s: string
    readonly foo: Foo
    }
    } // properties of Bar2 can't be reassigned

    let bar2 = new Bar2()

    bar2.n = 42 // <-- Error
    bar2.s = "foo" // <-- Error
    bar2.s.length = 0 // <-- Error
    bar2.foo = { // <-- Error
    n: 21,
    s: "bar"
    }
    bar2.foo.n = 42 // <-- Working
    bar2.foo.s = "foo" // <-- Working


    class Bar3 {
    n: Readonly<number>
    s: Readonly<string>
    n: Readonly<number> // has no effect
    s: Readonly<string> // has no effect
    foo: Readonly<Foo>
    }
    } // properties of Foo can't be reassigned

    let bar3 = new Bar3()

    bar3.n = 42 // <-- Working
    bar3.s = "foo" // <-- Working
    bar3.s.length = 0 // <-- Error
    bar3.foo = { // <-- Working
    n: 21,
    s: "bar"
    @@ -58,4 +62,16 @@ class Bar4 {
    readonly n: number
    readonly s: string
    readonly foo: Readonly<Foo>
    }
    } // Neither properties of Foo, nor Bar4 can't be reassigned

    let bar4 = new Bar4()

    bar4.n = 42 // <-- Error
    bar4.s = "foo" // <-- Error
    bar4.s.length = 0 // <-- Error
    bar4.foo = { // <-- Error
    n: 21,
    s: "bar"
    }
    bar4.foo.n = 42 // <-- Error
    bar4.foo.s = "foo" // <-- Error
  2. drothmaler created this gist May 6, 2020.
    61 changes: 61 additions & 0 deletions readonly.ts
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,61 @@

    interface Foo {
    n: number
    s: string
    }

    class Bar1 {
    n: number
    s: string
    foo: Foo
    }
    let bar1 = new Bar1()

    bar1.n = 42 // <-- Working
    bar1.s = "foo" // <-- Working
    bar1.foo = { // <-- Working
    n: 21,
    s: "bar"
    }
    bar1.foo.n = 42 // <-- Working
    bar1.foo.s = "foo" // <-- Working

    class Bar2 {
    readonly n: number
    readonly s: string
    readonly foo: Foo
    }
    let bar2 = new Bar2()

    bar2.n = 42 // <-- Error
    bar2.s = "foo" // <-- Error
    bar2.foo = { // <-- Error
    n: 21,
    s: "bar"
    }
    bar2.foo.n = 42 // <-- Working
    bar2.foo.s = "foo" // <-- Working


    class Bar3 {
    n: Readonly<number>
    s: Readonly<string>
    foo: Readonly<Foo>
    }
    let bar3 = new Bar3()

    bar3.n = 42 // <-- Working
    bar3.s = "foo" // <-- Working
    bar3.foo = { // <-- Working
    n: 21,
    s: "bar"
    }
    bar3.foo.n = 42 // <-- Error
    bar3.foo.s = "foo" // <-- Error


    class Bar4 {
    readonly n: number
    readonly s: string
    readonly foo: Readonly<Foo>
    }