implemented `FromStr` for `DateTime<FixedOffset/UTC>`.

src/datetime.rs

@@ -6,17 +6,18 @@
  * ISO 8601 date and time.
  */
 
-use std::{fmt, hash};
+use std::{str, fmt, hash};
 use std::cmp::Ordering;
 use std::ops::{Add, Sub};
 
 use {Weekday, Timelike, Datelike};
-use offset::{Offset, FixedOffset};
+use offset::{Offset, FixedOffset, UTC};
 use duration::Duration;
 use naive::datetime::NaiveDateTime;
 use time::Time;
 use date::Date;
-use format::{parse, Item, Parsed, ParseResult, DelayedFormat, StrftimeItems};
+use format::{Item, Numeric, Pad, Fixed};
+use format::{parse, Parsed, ParseError, ParseResult, DelayedFormat, StrftimeItems};
 
 /// ISO 8601 combined date and time with timezone.
 #[derive(Clone)]
@@ -261,6 +262,45 @@ impl<Off: Offset + fmt::Display> fmt::Display for DateTime<Off> {
     }
 }
 
+impl str::FromStr for DateTime<FixedOffset> {
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> ParseResult<DateTime<FixedOffset>> {
+        const ITEMS: &'static [Item<'static>] = &[
+            Item::Space(""), Item::Numeric(Numeric::Year, Pad::Zero),
+            Item::Space(""), Item::Literal("-"),
+            Item::Space(""), Item::Numeric(Numeric::Month, Pad::Zero),
+            Item::Space(""), Item::Literal("-"),
+            Item::Space(""), Item::Numeric(Numeric::Day, Pad::Zero),
+            Item::Space(""), Item::Literal("T"), // XXX shouldn't this be case-insensitive?
+            Item::Space(""), Item::Numeric(Numeric::Hour, Pad::Zero),
+            Item::Space(""), Item::Literal(":"),
+            Item::Space(""), Item::Numeric(Numeric::Minute, Pad::Zero),
+            Item::Space(""), Item::Literal(":"),
+            Item::Space(""), Item::Numeric(Numeric::Second, Pad::Zero),
+                             Item::Fixed(Fixed::Nanosecond),
+            Item::Space(""), Item::Fixed(Fixed::TimezoneOffsetZ),
+            Item::Space(""),
+        ];
+
+        let mut parsed = Parsed::new();
+        try!(parse(&mut parsed, s, ITEMS.iter().cloned()));
+        parsed.to_datetime()
+    }
+}
+
+impl str::FromStr for DateTime<UTC> {
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> ParseResult<DateTime<UTC>> {
+        // we parse non-UTC time zones then convert them into UTC
+        let dt: DateTime<FixedOffset> = try!(s.parse());
+        Ok(dt.with_offset(UTC))
+    }
+}
+
+// TODO: FromStr for DateTime<Local> is quite hard without a new offset design
+
 #[cfg(test)]
 mod tests {
     use super::DateTime;
@@ -294,6 +334,21 @@ mod tests {
         assert!(*EDT.ymd(2014, 5, 6).and_hms(7, 8, 9).offset() != EST);
     }
 
+    #[test]
+    fn test_datetime_from_str() {
+        assert_eq!("2015-2-18T23:16:9.15Z".parse::<DateTime<FixedOffset>>(),
+                   Ok(FixedOffset::east(0).ymd(2015, 2, 18).and_hms_milli(23, 16, 9, 150)));
+        assert_eq!("2015-2-18T13:16:9.15-10:00".parse::<DateTime<FixedOffset>>(),
+                   Ok(FixedOffset::west(10 * 3600).ymd(2015, 2, 18).and_hms_milli(13, 16, 9, 150)));
+        assert!("2015-2-18T23:16:9.15".parse::<DateTime<FixedOffset>>().is_err());
+
+        assert_eq!("2015-2-18T23:16:9.15Z".parse::<DateTime<UTC>>(),
+                   Ok(UTC.ymd(2015, 2, 18).and_hms_milli(23, 16, 9, 150)));
+        assert_eq!("2015-2-18T13:16:9.15-10:00".parse::<DateTime<UTC>>(),
+                   Ok(UTC.ymd(2015, 2, 18).and_hms_milli(23, 16, 9, 150)));
+        assert!("2015-2-18T23:16:9.15".parse::<DateTime<UTC>>().is_err());
+    }
+
     #[test]
     fn test_datetime_parse_from_str() {
         let ymdhms = |&: y,m,d,h,n,s,off| FixedOffset::east(off).ymd(y,m,d).and_hms(h,n,s);

src/lib.rs

@@ -146,16 +146,21 @@ assert_eq!(dt.to_string(), "2014-11-28 12:00:09 UTC");
 assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
 ~~~~
 
-Parsing can be done with two methods:
+Parsing can be done with three methods:
 
-- `DateTime::parse_from_str` parses a date and time with offsets and
-  returns `DateTime<FixedOffset>`.
-  This should be used when the offset is a part of input and the caller cannot guess that.
-  It *cannot* be used when the offset can be missing.
+1. The standard `FromStr` trait (and `parse` method on a string) can be used for
+   parsing `DateTime<FixedOffset>` and `DateTime<UTC>` values.
+   This parses what the `{:?}` (`std::fmt::Debug`) format specifier prints,
+   and requires the offset to be present.
 
-- `Offset::datetime_from_str` is similar but returns `DateTime` of given offset.
-  When the explicit offset is missing from the input, it simply uses given offset.
-  It issues an error when the input contains an explicit offset different from the current offset.
+2. `DateTime::parse_from_str` parses a date and time with offsets and
+   returns `DateTime<FixedOffset>`.
+   This should be used when the offset is a part of input and the caller cannot guess that.
+   It *cannot* be used when the offset can be missing.
+
+3. `Offset::datetime_from_str` is similar but returns `DateTime` of given offset.
+   When the explicit offset is missing from the input, it simply uses given offset.
+   It issues an error when the input contains an explicit offset different from the current offset.
 
 More detailed control over the parsing process is available via `format` module.
 
@@ -163,8 +168,16 @@ More detailed control over the parsing process is available via `format` module.
 use chrono::{UTC, Offset, DateTime};
 
 let dt = UTC.ymd(2014, 11, 28).and_hms(12, 0, 9);
+
+// method 1
+assert_eq!("2014-11-28T12:00:09Z".parse::<DateTime<UTC>>(), Ok(dt.clone()));
+assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<UTC>>(), Ok(dt.clone()));
+
+// method 2
 assert_eq!(UTC.datetime_from_str("2014-11-28 12:00:09", "%Y-%m-%d %H:%M:%S"), Ok(dt.clone()));
 assert_eq!(UTC.datetime_from_str("Fri Nov 28 12:00:09 2014", "%a %b %e %T %Y"), Ok(dt.clone()));
+
+// method 3
 assert_eq!(DateTime::parse_from_str("2014-11-28 21:00:09 +09:00",
                                     "%Y-%m-%d %H:%M:%S %z").map(|dt| dt.with_offset(UTC)), Ok(dt));