Added RKDotNetDateFormatter to translate back and forth between NSDate and strings like /Date(1234567890123-0500)/ Also includes header docs and specs. Fixes #264

Code/Support/RKDotNetDateFormatter.h

@@ -0,0 +1,57 @@
+//
+//  RKDotNetDateFormatter.h
+//  RestKit
+//
+//  Created by Greg Combs on 9/8/11.
+//  Copyright (c) 2011 RestKit. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+/**
+ A subclass of NSDateFormatter that serves as translator between ASP.NET date serializations in JSON
+ strings and NSDate objects. This is useful for properly mapping these dates from an ASP.NET driven backend.
+ *NOTE* - DO NOT attempt to use setDateFormat: on this class.  It will return invalid results.
+ */
+@interface RKDotNetDateFormatter : NSDateFormatter {
+    NSRegularExpression *dotNetExpression;
+}
+
+/**
+ Returns an NSDate object from an ASP.NET style date string respresentation, as seen in JSON.
+ Acceptable examples are:
+    /Date(1112715000000-0500)/
+    /Date(1112715000000)/
+ Where 1112715000000 is the number of milliseconds since January 1, 1970 00:00 GMT/UTC, and -0500 represents the
+ timezone offset from GMT in 24-hour time.  
+ 
+ *NOTE* NSDate objects do not have timezones, and you should never change an actual date value based on a
+ timezone offset.  However, timezones are important when presenting dates to the user.  Therefore,
+ If an offset is present in the ASP.NET string (it should be), we actually ignore the offset portion because 
+ we want to store the actual date value in its raw form, without any pollution of timezone information.  
+ If, on the other hand, there is no offset in the ASP.NET string, we assume GMT (+0000) anyway.
+ In summation, for this class setTimeZone: is ignored except when using stringFromDate: 
+ 
+ @param string The ASP.NET style string, /Date(1112715000000-0500)/
+ @return An NSDate object
+ @see stringFromDate
+ @see NSDateFormatter
+ @see NSTimeZone
+ */
+- (NSDate *)dateFromString:(NSString *)string;
+
+/**
+ Returns an ASP.NET style date string from an NSDate, such as /Date(1112715000000+0000)/
+ Where 1112715000000 is the number of milliseconds since January 1, 1970 00:00 GMT/UTC, and +0000 is the
+ timezone offset from GMT in 24-hour time.  
+ 
+ *NOTE* GMT (+0000) is assumed otherwise specified via setTimeZone:
+ 
+ @param date An NSDate
+ @return The ASP.NET style string, /Date(1112715000000-0500)/
+ @see dateFromString
+ @see NSDateFormatter
+ @see NSTimeZone
+ */
+- (NSString *)stringFromDate:(NSDate *)date;
+@end

Code/Support/RKDotNetDateFormatter.m

@@ -0,0 +1,92 @@
+//
+//  RKDotNetDateFormatter.m
+//  RestKit
+//
+//  Created by Greg Combs on 9/8/11.
+//  Copyright (c) 2011 RestKit. All rights reserved.
+//
+
+#import "RKDotNetDateFormatter.h"
+#import "RestKit.h"
+
+BOOL isValidRange(NSRange rangeOfMatch);
+NSTimeInterval secondsFromMilliseconds(NSTimeInterval millisecs);
+NSTimeInterval millisecondsFromSeconds(NSTimeInterval seconds);
+
+@interface RKDotNetDateFormatter()
+- (NSString *)millisecondsFromString:(NSString *)string;
+@end
+
+@implementation RKDotNetDateFormatter
+
+- (NSDate *)dateFromString:(NSString *)string {
+    NSString *milliseconds = [self millisecondsFromString:string];
+    if (!milliseconds) {
+        RKLogError(@"Attempted to interpret an invalid .NET date string: %@", string);
+        return nil;
+    }
+    NSTimeInterval seconds = secondsFromMilliseconds([milliseconds doubleValue]);
+    return [NSDate dateWithTimeIntervalSince1970:seconds];
+}
+
+
+- (NSString *)stringFromDate:(NSDate *)date {
+    if (!date) {
+        RKLogError(@"Attempted to represent an invalid date: %@", date);
+        return nil;
+    }
+    NSTimeInterval milliseconds = millisecondsFromSeconds([date timeIntervalSince1970]);
+    NSString *timeZoneOffset = [super stringFromDate:date];
+    return [NSString stringWithFormat:@"/Date(%1.0lf%@)/", milliseconds, timeZoneOffset];
+}
+
+
+- (id)init {
+    self = [super init];
+    if (self) {
+        self.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease];
+        self.timeZone = [NSTimeZone timeZoneWithName:@"UTC"];
+        [self setDateFormat:@"ZZ"]; // GMT offset, like "-0500"
+        NSString *pattern = @"\\/Date\\((\\d+)((?:[\\+\\-]\\d+)?)\\)\\/"; // /Date(mSecs)/ or /Date(mSecs-0400)/
+        dotNetExpression = [[NSRegularExpression alloc] initWithPattern:pattern options:NSRegularExpressionCaseInsensitive error:NULL];
+    }
+    return self;
+}
+
+
+- (void)dealloc {
+    [dotNetExpression release];
+    [super dealloc];
+}
+
+
+- (NSString *)millisecondsFromString:(NSString *)string {
+    if (!string)
+        return nil;
+    NSTextCheckingResult *match = [dotNetExpression firstMatchInString:string options:NSMatchingCompleted range:NSMakeRange(0, [string length])];
+    if (!match)
+        return nil;
+    NSRange millisecRange = [match rangeAtIndex:1];
+    if (!isValidRange(millisecRange))
+        return nil;
+    //NSRange timeZoneRange = [match rangeAtIndex:2];
+    NSString *milliseconds = [string substringWithRange:millisecRange];
+    return milliseconds;
+}
+@end
+
+
+BOOL isValidRange(NSRange rangeOfMatch) {
+    return (!NSEqualRanges(rangeOfMatch, NSMakeRange(NSNotFound, 0)));
+}
+
+
+NSTimeInterval secondsFromMilliseconds(NSTimeInterval millisecs) {
+    return millisecs / 1000.f;
+}
+
+
+NSTimeInterval millisecondsFromSeconds(NSTimeInterval seconds) {
+    return seconds * 1000.f;
+}
+

Code/Support/Support.h

@@ -12,3 +12,4 @@
 #import "RKLog.h"
 #import "NSString+RestKit.h"
 #import "RKPathMatcher.h"
+#import "RKDotNetDateFormatter.h"