Hi Adrian,
"\(key)" is already part of Swift (see
<https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/StringsAndCharacters.html#//apple_ref/doc/uid/TP40014097-CH7-ID285>).
Maybe using "<\(quote)> by <\(person)>" as example was not the best
idea, I should have used "“\(quote)” by \(person)". I changed the gist
accordingly.
On 2016-04-21 11:21, Adrian Zubarev wrote:
I took a quick look at your proposal and one thing I didn’t liked
was the string itsel: "some text <\(key)>“
This looks odd to me. I’d suggest something like "some text
@(key)“ or "some text \[key]“ instead. But it is not up to me.
--
Adrian Zubarev
Am 21. April 2016 bei 09:42:18, Daniel Höpfl via swift-evolution
([email protected]) schrieb:
Hi there!
TL;DR: Here’s my idea for a better localized strings handling in
Swift.
It includes both, support for string interpolation support for
NSLocalizedString, and a new string delimiter `...` that can be used
instead of NSLocalizedString("...").
Markdown hard to read? See
<https://gist.github.com/dhoepfl/203f8b9bb8014593772a3b12d807ebce>
Greetings,
Daniel
# Localization support for string interpolation
## Introduction
I'd like to see some kind of advanced localization support in the
Swift
standard library. Currently all we have is what Cocoa provides but
that
does not work well with string interpolation. More or less, you can
not
use string interpolation if you have to use `NSLocalizedString` and
friends.
[I implemented a proof of
concept](https://github.com/dhoepfl/DHLocalizedString),
`DHLocalizedString`, that fills this gap. I would like to see
something
similar being part of the Swift standard library. While it is
possible
to implement localized strings as a custom library, this lacks
support
from genstring and other tools.
I’m not sure if `NSLocalizedString` is considered part of the
Swift
standard library (being part of Foundation Functions). Since there
is
decent Unicode-string support in Swift, I would like to see
localization
as part of the language, too. This proposal also includes a new
string
delimiter `` ` `` that deeply integrate localized strings in the
language.
## Motivation
String interpolation greatly simplyfies text handling but makes it
hard
to localize. You can not pass a string with interpolation to
`NSLocalizedString` because the key could be unpredictable.
## Proposed solution
`NSLocalizedString` should be extended to work with string
interpolation:
```swift
let quote = "Never trust the internet!"
let person = "Albert Einstein"
print(NSLocalizedString("<\(quote)> by <\(person)>"));
```
should look up the key:
```"<%@> by <%@>" = "%2$@ said: “%1$@”";```
and print:
```Albert Einstein said: “Never trust the internet!”```
So, `NSLocalizedString` (and friends) would “just work” with
string
interpolation. I’m not sure about the key format to use but my
proof of
concept simply replaces every interpolation with `%@` which seems
reasonable.
The proof of concept also includes an postfix operator `|~` (think
of a
flag) to reduce the impact localized strings have in line length.
Actually, I would love to replace `"` by a different marker (e.g.
`~|string|~`, `''string''`, ``` ``string`` ```, or `` `string` ``?)
for
localized strings. Imagine you could write the previous example as:
```swift
print(`<\(quote)> by <\(person)>`);
```
This syntax needs some work on how to specify `tableName:`,
`bundle:`,
and `comment:`. For `tableName:` and `bundle:`, I'd love to have a
construct to specify it for all localization tags within the file
(e.g.
`#localization(tableName: ..., bundle: ...)`).
If Swift gets multiline strings (`"""string"""`), `` `string` ``
could
also have ```` ```multiline``` ````.
## Impact on existing code
I see very little impact. There might be code out there that uses a
interpolated string as argument for `NSLocalizedString`. The key
used in
this case would change, breaking the translation. It would be
possible
to include a check for interpolated strings as arguments to
`NSLocalizedString` calls in the code update tool.
## Alternatives considered
### Use `NSLocalizedString` as is
One can use `NSLocalizedString` as it was used in Objective-C but
this
means that string interpolation cannot be used.
### `localized()` function for String class
I did not find a way how to get the function called before the
string
interpolation took place. (`"<\(quote)> by
<\(person)>".localized()`)
### Custom function
See above: The drawbacks are: Not having support in standard tools
and
the operator syntax not being as good as it could be.
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