In C# we have CultureInfo which affects the way ToString() works for dates and numbers
eg. you can set CurrentCulture by doing:
Thread.CurrentThread.CurrentCulture = new CultureInfo("pl-PL");;
Is there any equivalent for the above in dart?
EDIT:
Short answer is: use intl package (thanks to all for answers)
As Alan Knight pointed below setting locale "by thread" does not make sense in Dart since we do not control threads explicite.
At the moment i write this NumberFormating is work in progress as far as i understand it
The intl library will offer you this, although it doesn't affect the behavior of toString().
Here's an example:
Add as a dependency to your pubspec.yaml:
dependencies:
intl: any # You might specify some version instead of _any_
Then a code sample:
import 'package:intl/intl.dart';
import 'package:intl/date_symbol_data_local.dart';
main() {
initializeDateFormatting("en_US", null).then((_) {
var formatter = new DateFormat.yMd().add_Hm();
print(formatter.format(new DateTime.now()));
});
}
The output looks like this:
07/10/1996 12:08 PM
Yes, as per the previous entry the Intl library is what you want. You can set the default locale, or use the withLocale method to set it within a function. Setting it by thread doesn't work, as there are no threads. The other major difference is that, since this is all downloaded into the browser, you don't automatically have all the locale data available, but have to go through an async initialization step to load the data. That will probably be switched over to use the new lazy loading features soon.
Also, the locale doesn't affect the system toString() operation but rather you have to use a DateFormat object to print the date. And as it's still work in progress, NumberFormat doesn't work properly for locales yet, but should soon.
http://api.dartlang.org/docs/releases/latest/intl/Intl.html
From the page:
The Intl class provides a common entry point for internationalization related tasks.
Related
I have a Dart class (foo.dart):
class Foo {
void talk() {
print('Hello');
}
}
After compiling foo.dart to JavaScript, I'd like to be able to use Foo like this:
var foo = new Foo(); // from foo.dart.js
foo.talk() // prints "Hello"
My questions:
Is this currently possible?
If so, how?
If not, what plans, if any, are in place to make it possible?
The dart:js library documentation states:
This library does not yet make Dart objects usable from JavaScript, their methods and proeprties [sic] are not accessible, though it does allow Dart functions to be passed into and called from JavaScript.
That word "yet" offers some hope, but I've found very little on this topic anywhere else.
Edit:
I do realize it's possible to call Dart functions from JavaScript using dart2js. However, what I'm trying to do is somewhat different. I'd like to be able to access all of the functionality of a Dart class from JavaScript.
Due to tree-shaking and minification this is normally not possible. If you have a Dart application (with a main() then you can make a Dart function available to be called from JavaScript (see How to call a Dart function from Javascript? for an example).
As far as I know there are plans to support your requirement but I have no idea about progress or when such a feature might be available.
This is the related project https://github.com/dart-lang/js-interop
Initial Googling indicates that there's no built-in way to do regular expressions in an Objective-C Cocoa application.
So four questions:
Is that really true?
Are you kidding me?
Ok, then is there a nice open-source library you recommend?
What are ways to get close enough without importing a library, perhaps with the NSScanner class?
I noticed that as of iOS 4.0 Apple provides a NSRegularExpression class. Additionally, as of 10.7, the class is available under OS X.
Yes, there's no regex support in Cocoa. If you're only interested in boolean matching, you can use NSPredicate which supports ICU regex syntax. But usually you're interested in the position of the match or position of subexpressions, and you cannot get it with NSPredicate.
As mentioned you can use regex POSIX functions. But they are considered slow, and the regex syntax is limited compared to other solutions (ICU/pcre).
There are many OSS libraries, CocoaDev has an extensive list.
RegExKitLite for example doesn't requires any libraries, just add the .m and .h to your project.
(My complaint against RegExKitLite is that it extends NSString via category, but it can be considered as a feature too. Also it uses the nonpublic ICU libraries shipped with the OS, which isn't recommended by Apple.)
RegexKit is the best I've found yet. Very Cocoa:y. I'm using the "Lite" version in several of our iPhone apps:
sourceforge
lingonikorg
You can use the POSIX Regular Expressions library (Yay for a POSIX compliant OS). Try
man 3 regex
The cheap and dirty hack solution that I use to solve REGEX and JSON parsing issues is to create a UIWebView object and inject Javascript function(s) to do the parsing. The javascript function then returns a string of the value (or list of values) I care about. In fact, you can store a small library set of functions customized for particular tasks and then just call them as needed.
I don't know if it this technique scales to huge volumes of repeated parsing requests, but for quick transactional stuff it gets the job done without depending on any extra external resources or code you might not understand.
I like the AGRegex framework which uses PCRE, handy if you are used to the PCRE syntax. The best version of this framework is the one in the Colloquy IRC client as it has been upgraded to use PCRE 6.7:
http://colloquy.info/project/browser/trunk/Frameworks/AGRegex
It's very lightweight, much more so than RegExKit (although not as capable of course).
NSRegularExpression is available since Mac OS X v10.7 and IOS 4.0.
During my search on this topic I came across CocoaOniguruma which uses Oniguruma, the Regular Expression engine behind Ruby1.9 and PHP5. It seems a bit newer compared to the existing OregKit (in Japanese). Not sure how these stack up against other bindings.
Googling alittle, found this library:
RegexOnNSString
Open source library, containing functions like:
-(NSString *) stringByReplacingRegexPattern:(NSString *)regex withString:(NSString *) replacement caseInsensitive:(BOOL)ignoreCase
and using NSRegularExpression class. Quite easy to use and no need to worry about anything.
Please, note that NSRegularExpression is available since Mac OS X v10.7 and IOS 4.0, as Datasmid mentioned.
I make it easy. I add a new C++ file to my Objective C project, rename it as .mm, and then create a standard C++ class inside. Then, I make a static class method in the "public:" section for a C++ function that takes an NSString and returns an NSString (or NSArray, if that's what you want). I then convert NSString to C++ std::string like so:
// If anyone knows a more efficient way, let me know in the comments.
// The "if" condition below is because ObjC crashes if converting to
// std::string if the string is nil or empty.
// assume #include <string>
std::string s = "";
if (([sInput != nil]) && (!([sInput isEqualTo:#""]))) {
std::string sTemp([sInput UTF8String]);
s = sTemp;
}
From there, I can use regex_replace like so:
// assume #include <regex>
std::string sResult = std::regex_replace(sSource,sRegExp,sReplaceWith);
Then, I can convert that std::string back into an NSString with:
NSString *sResponse2 = #(sResult.c_str());
If you're only using this C++ just for this function, then you may find it suitable to call this file extra.mm (class name Extra) and put this static class method in, and then add other static class methods when the situation arrives where it just makes sense to do it in C++ because it's less hassle in some cases. (There are cases where ObjC does something with less lines of code, and some cases where C++ does it with less lines of code.)
P.S. Still yet another way with this is to use a .mm file but make an Objective C wrapper around the use of std::string and std::regex_replace() (or regex_match()).
I would like to know how can I build a clock (date and current time) using Dart. I'll be binding the resulting observable string (so it refreshes automatically) to an HTML Polymer element.
I thought about using a timer to refresh the string using DateTime.now(), but this seems to be a workaround, not the best solution.
I just need to know how to code the dart file, since the HTML and Polymer elements are already configured.
You might take a look at this example
https://github.com/bwu-dart/polymer_ui_elements/blob/master/example/polymer_ui_clock.html
https://github.com/bwu-dart/polymer_ui_elements/blob/master/lib/polymer_ui_clock/polymer_ui_clock.dart
It needs a little tweaking to work with the current Polymer version.
var oneSecond = new Duration(seconds: 1);
_timer = new Timer.periodic(oneSecond, updateTime);
updateTime is a method called every second.
I am trying to use Dart to tersely define entities in an application, following the idiom of code = configuration. Since I will be defining many entities, I'd like to keep the code as trim and concise and readable as possible.
In an effort to keep boilerplate as close to 0 lines as possible, I recently wrote some code like this:
// man.dart
part of entity_component_framework;
var _man = entity('man', (entityBuilder) {
entityBuilder.add([TopHat, CrookedTeeth]);
})
// test.dart
part of entity_component_framework;
var man = EntityBuilder.entities['man']; // null, since _man wasn't ever accessed.
The entity method associates the entityBuilder passed into the function with a name ('man' in this case). var _man exists because only variable assignments can be top-level in Dart. This seems to be the most concise way possible to use Dart as a DSL.
One thing I wasn't counting on, though, is lazy initialization. If I never access _man -- and I had no intention to, since the entity function neatly stored all the relevant information I required in another data structure -- then the entity function is never run. This is a feature, not a bug.
So, what's the cleanest way of using Dart as a DSL given the lazy initialization restriction?
So, as you point out, it's a feature that Dart doesn't run any code until it's told to. So if you want something to happen, you need to do it in code that runs. Some possibilities
Put your calls to entity() inside the main() function. I assume you don't want to do that, and probably that you want people to be able to add more of these in additional files without modifying the originals.
If you're willing to incur the overhead of mirrors, which is probably not that much if they're confined to this library, use them to find all the top-level variables in that library and access them. Or define them as functions or getters. But I assume that you like the property that variables are automatically one-shot. You'd want to use a MirrorsUsed annotation.
A variation on that would be to use annotations to mark the things you want to be initialized. Though this is similar in that you'd have to iterate over the annotated things, which I think would also require mirrors.
Seth Ladd's Polymer.dart examples are awesome and really helpful. The observable_list example appends DateTime instances to an ObservableList timestamps. Although DateTime does not extend Observable, modifying my_element.html to access a field on
{{ts in timestamps}}
works when running in the Dart VM. For example, changing
<li>{{ts}}</li>
to
<li>{{ts.second}}</li>
will access the DateTime.seconds field when on the Dart VM. However, when dart2js compiles the app to javascript, access to fields in the Polymer expression is broken. An exception Uncaught Error: RangeError: value 0 is thrown in this case, or more generally NoSuchMethodError : method not found: 'Symbol(...)' for the fieldname is thrown (see example here)
If a class extends Observable then access to #observable fields works inside of Polymer expressions after compiling to Javascript (changing the class MyRow in this example to extends Observable does not throw an exception in javascript).
What can I do when I am unable to add annotations to external classes like DateTime? Is this just a current bug in dart2js generation, or will the Polymer.dart spec forbid reading fields out of non-observable classes? Previously, web_ui successfully accessed fields from our dart-protobuf generated classes after compiling to javascript, so I'm hoping this use-case will gain support in Polymer.dart too.
In general, dart2js tries to tree-shake and minify code, and it doesn't know that some of the code is used from a polymer expression (which uses mirrors internally to interpret the expressions). Very likely what happened here is that dart2js is either deleting the non-observable fields or minifying them in a way that they are not reflectable.
To fix this, you can indicate that these fields need to be preserved and used via mirrors. In polymer we provide the #reflectable annotation for this purpose. (#observable also implies #reflectable, that's why it works when you have #observable). So you can use that in the MyRow case.
Fields from types in the core libraries can work also if they become reflectable. In this case it is a bit harder to express because you can't modify the original code to add this annotation. Instead you can use the #MirrorsUsed annotation to override the default behavior on these core types, or avoid using these fields inside polymer-expressions by hiding them inside #reflectable getters or in filters that are written directly in Dart code.