Is ForEach loop the only loop that's allowed inside a view?

Question

TurtleLover OP

Created Oct ’20

Replies 3

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I always get errors whenever I use the normal for loop and the repeat loop.

Answered by OOPer in 638956022

Is ForEach loop the only loop that's allowed inside a view?

As for now, YES.

To allow declarative syntax inside a view, view construction is made under the context of ViewBuilder.
The current implementation of ViewBuilder is based on @_functionBuilder, which is an Apple's original enhancement to Swift and does not permit for-in loop or repeat inside it.

It will be replaced by Swift Standard @resultBuilder in the near future. The new @resultBuilder would accept for-in loops in some specific cases, but it would not allow repeat inside.

SE-0289 Result builders

If you have some view construction logic in mind using for-in or repeat, you should better be accustomed to replace it using ForEach. No new feature would be added to @resultBuilder in the near future.

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Answer 1

OOPer OP

Oct ’20

Accepted Answer

Is ForEach loop the only loop that's allowed inside a view?

As for now, YES.

To allow declarative syntax inside a view, view construction is made under the context of ViewBuilder.
The current implementation of ViewBuilder is based on @_functionBuilder, which is an Apple's original enhancement to Swift and does not permit for-in loop or repeat inside it.

It will be replaced by Swift Standard @resultBuilder in the near future. The new @resultBuilder would accept for-in loops in some specific cases, but it would not allow repeat inside.

SE-0289 Result builders

If you have some view construction logic in mind using for-in or repeat, you should better be accustomed to replace it using ForEach. No new feature would be added to @resultBuilder in the near future.

2

Answer 2

TurtleLover OP

Oct ’20

Thanks, OOPer. Do we know when this update will be released?

1

Answer 3

OOPer OP

Oct ’20

Do we know when this update will be released?

Hard to predict, as well as the behavior of SwiftUI.

https://forums.swift.org/t/se-0289-review-2-result-builders/40585/

Depends on how Evolution process of Swift would go.
I expect in a month or so, but it might be later.

1