SwiftUI View require body and some keyword question

maomao · August 2, 2019, 7:42am

I have a question about some keyword and body

When you create a struct and you have to add them in the struct.

Does anyone know why we have to and what does some keyword mean?

Thanks

jayantvarma · August 5, 2019, 7:40am

Hi @maomao,
You might want to read up on Opaque return, this is the opposite of Generics. The easiest and simplest way to describe some is that it expects a return to be of a particular type. In SwiftUI everything is a View and therefore the return type expects that it will be a View of some type. Not specifying a Button, Text, or another specific type.

That’s the best in short explanation, I hope that helps

cheers,

maomao · August 5, 2019, 9:25am

Thank jay I got it haha. What does Generics and Opaque mean?

jayantvarma · August 5, 2019, 9:27am

Hi @maomao,
No problems, here’s the proposal about Opaque Return types from Apple

github.com

apple/swift-evolution/blob/main/proposals/0244-opaque-result-types.md

# Opaque Result Types

* Proposal: [SE-0244](0244-opaque-result-types.md)
* Authors: [Doug Gregor](https://github.com/DougGregor), [Joe Groff](https://github.com/jckarter)
* Review Manager: [Ben Cohen](https://github.com/airspeedswift)
* Status: **Implemented (Swift 5.1)**
* Implementation: [apple/swift#22072](https://github.com/apple/swift/pull/22072)
* Toolchain: https://github.com/apple/swift/pull/22072#issuecomment-483495849
* Previous revisions: ([1](https://github.com/apple/swift-evolution/commit/e60bac23bf0d6f345ddb48fbf64ea8324fce79a9))
* Previous review threads: https://forums.swift.org/t/se-0244-opaque-result-types/21252
* Decision Notes: [Rationale](https://forums.swift.org/t/se-0244-opaque-result-types-reopened/22942/57)

## Introduction

This proposal is the first part of a group of changes we're considering in a [design document for improving the UI of the generics model](https://forums.swift.org/t/improving-the-ui-of-generics/22814). We'll try to make this proposal stand alone to describe opaque return types, their design, and motivation, but we also recommend reading the design document for more in-depth exploration of the relationships among other features we're considering. We'll link to relevant parts of that document throughout this proposal.

This specific proposal addresses the problem of [type-level abstraction for returns](https://forums.swift.org/t/improving-the-ui-of-generics/22814#heading--missing-type-level-abstraction). Many libraries consist of composable generic components. For example, a graphics library might provide primitive types for basic shapes:

```swift
protocol Shape {

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maomao · August 6, 2019, 9:47am

Thanks I will take a look I realised that Jay is from Melbourne as well haha and I bought Swift book here.

jayantvarma · August 7, 2019, 10:22am

@maomao, cool have we met at Cocoaheads or otherwise?

maomao · August 7, 2019, 11:12am

not yet I think we will meet soon

uwilly · August 9, 2019, 6:51am

The some keyword is to say you function or property will always return the same actually type, for example if you declare a method that returns some Equatable, you won’t return Float on some calls and Int on others, without that there is no way to do an == between the result of two calls to your function because there is no way for the compiler to know if they are both of the same, since they could be any Equatable.

system · January 15, 2020, 11:42pm

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