Can Optional Chaining imitate swift style?

[0x30]

TypeScript - issues 34970

I think I should bring it up here

Search Terms

• swift style
• Swift if let statement
• Optional Chaining

Suggestion

1. The left-hand side of an assignment expression may not be an optional property acces
2. if let style,determine whether it is optional and obtain the object

Use Cases

for Suggestion 1

The following code is not allowed in typescript 3.7.2.It's going to make a The left-hand side of an assignment expression may not be an optional property access mistake

class Foo{
  foo: Foo | undefined
  name: String | undefined
}
let foo = new Foo()
 // next line. ~~ The left-hand side of an assignment expression may not be an optional property access
foo.foo?.name = "";

But similar code, swift works well

class Foo{
    var name: String?
    var foo: Foo?
}
let foo = Foo()
foo.foo?.name = "hello"

In view of this, do we have any plans to solve this problem at present?

for Suggestion 2

About judging optional variables and using it,The current practice of TS is

if(foo?.foo) {
    /// foo.foo is non optional
}

In swift, there is a way to turn optional into non optional.

if let foo1 = foo?.foo {
   // -- foo1 is non optional
}

Can be used in 'kotlin'

foo?.foo?.let{ foo1 -> 
   // -- foo1 is non optional
}

If you judge a method result. In order not to call the calculation twice, you need to replace the code with.

const value = foo?.foo()
if(value) {
    // -- value is non optional
}

[jridgewell]

foo.foo?.name = "hello"

Optional assignment is discussed in #18.

if let foo1 = foo?.foo { … }

See https://github.com/tc39/proposal-Declarations-in-Conditionals

[0x30]

foo.foo?.name = "hello"

Optional assignment is discussed in #18.

if let foo1 = foo?.foo { … }

See https://github.com/tc39/proposal-Declarations-in-Conditionals

@jridgewell ok. thanks. I went to have a look. The proposal is already very good

[claudepache]

Closing this issue per #126 (comment) above.