api: introducing the now_with_time_zone for Zoned #94
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BurntSushi
requested changes
Aug 12, 2024
src/zoned.rs
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| /// use jiff::{Timestamp, Zoned}; | ||
| /// use jiff::tz::TimeZone; | ||
| /// | ||
| /// assert!(Zoned::now_with_time_zone(TimeZone::UTC).timestamp() > Timestamp::UNIX_EPOCH); |
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Can you make sure this is wrapped to 79 columns (inclusive)? Probably like this:
let zdt = Zoned::now_with_time_zone(TimeZone::UTC);
assert!(zdt.timestamp() > Timestamp::UNIX_EPOCH);| @@ -413,6 +413,40 @@ impl Zoned { | |||
| .expect("system time is valid") | |||
| } | |||
|
|
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| /// Returns the current system time with the specific time zone. | |||
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Can you add that this is a convenience function for Zoned::new(Timestamp::now(), time_zone)?
1996fanrui
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Aug 12, 2024
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Thanks @BurntSushi for the quick review!
All commnets are addressed :)
BurntSushi
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Aug 12, 2024
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This PR adds a note to the `Zoned::now()` documentation describing the best way to create a `Zoned` for the current time in a time zone that isn't the system time zone. Unfortunately, one intuitive route is `Zoned::now().with_time_zone()`, but this 1) fetches the system time zone, which isn't free and 2) computes the civil datetime for the system time zone, which is not necessary here. Instead, `Timestamp::now().to_zoned()` is a more direct approach that doesn't do any unnecessary work. I decided to go this route instead of adding a new API as requested in #93. In particular, I think the API suggested in #93 is a bit clunky, and is likely to lead to the addition of other even clunkier APIs as well. While using a `Timestamp` might require an extra import, it does have the benefit of being compositional. I'd like to encourage that instead of adding a bunch of alternative constructors. Moreoever, I feel like the Jiff API overall does a good job of avoiding lots of different constructors that I usually find somewhat confusing in other APIs. We might eventually have to give into that depending on use cases, but I think for this here, a documentation note suffices. Closes #93, Closes #94
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close #93
Currently, Zoned has now funcation to return the current system time in this system's time zone. I propose to introduce the now_with_time_zone for Zoned.
It's needed for some reasons:
How to create a now Zoned with specific time zone for current code?
Zoned::now(Solution2) has clearer semantics for developers, but it requires repeated creation of TimeZone objects. (Zoned::now needs to clone a default TimeZone, and with_time_zone also requires a TimeZone).I have a benchmark for them[2]:
- The avg time solution 1 is 297.61 ns
- The avg time solution 2 is 443.87 ns
- 297.61 ns * 151% = 443.87 ns, so performance of solution 1 is totally better than solution2.
The ZonedDateTime[3] of Java has 3 now functions, it includes now(), now(ZoneId) and now(Clock). It's useful for developers.
[1] https://github.com/fast/logforth/blob/b2d5e7e664595f58d35377136b4936fc4ac22c3f/src/layout/text.rs#L89
[2] https://github.com/1996fanrui/fanrui-learning/blob/aacfa73de1a2299745241806f61aa098d0b66a23/rust-learning/benches/jiff_benchmark.rs#L6
[3] https://docs.oracle.com/en%2Fjava%2Fjavase%2F11%2Fdocs%2Fapi%2F%2F/java.base/java/time/ZonedDateTime.html#now(java.time.ZoneId)