Chapter 15, Exercise 1

skochan

Administrator
Hero Member

Posts: 3114

Chapter 15, Exercise 1

« on: August 19, 2011, 11:18:51 AM »

Post your solutions by replying to this topic.

Cheers,

Steve


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Bertus

Newbie

Posts: 18

'Audaces fortuna iuvat'

Re: Chapter 15, Exercise 1

« Reply #1 on: August 24, 2011, 06:29:44 AM »

Got it!

Code: (Objective-C)


//
//  main.m
//  Excerise15_1
//
//  Created by Bertus ten Hoor on 24-08-11.
//  Copyright 2011 Skooter jeans & fashion bv. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSDate (ElapsedDays) 

    -(unsigned long) elapsedDays: (NSDate *) theDate;

@end

@implementation NSDate (ElapsedDays)
    

-(unsigned long) elapsedDays: (NSDate *) theDate
{
    unsigned long result;
    
    result = [self timeIntervalSinceDate:theDate];
    
    return result/86400;  //convert seconds to days

}

@end

int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    NSDate *toDay = [NSDate date];     //sets toDay to today's date
    NSDate *dateToCompare = [NSDate dateWithString:@"2011-08-01 00:01:00 +0000"];     //any given date to compare to

    NSLog(@"The difference in days between %@ and %@ is %lu",toDay, dateToCompare, [toDay elapsedDays:dateToCompare]);

    [pool drain];
    return 0;
}


« Last Edit: August 24, 2011, 07:20:27 AM by Bertus »	Logged

Kevin D

Newbie

Posts: 5

Re: Chapter 15, Exercise 1

« Reply #2 on: August 26, 2011, 12:17:37 PM »

Homework

Code: (Objective-C)

//
//  NSDate.h
//  ch15ex1
//
//  Created by Kevin on 8/26/11.
//  Copyright 2011 Shoebox Apps, Inc. All rights reserved.
//

#import <Foundation/Foundation.h>


@interface NSDate (ElapsedDays)

- (unsigned long) elaspsedDays: (NSDate *) theDate;

@end

Code: (Objective-C)

//
//  NSDate.m
//  ch15ex1
//
//  Created by Kevin on 8/26/11.
//  Copyright 2011 Shoebox Apps, Inc. All rights reserved.
//

#import "NSDate.h"


@implementation NSDate (ElapsedDays)

- (unsigned long) elaspsedDays: (NSDate *) theDate
{
	unsigned long timeSince;
	timeSince = [self timeIntervalSinceDate:theDate];  // gives number in seconds
	int secsInDay = 86400; // The number of seconds in a day
	return timeSince/secsInDay;
}

@end

Code: (Objective-C)

//
//  main.m
//  ch15ex1
//
//  Created by Kevin on 8/26/11.
//  Copyright 2011 Shoebox Apps, Inc. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "NSDate.h"

int main (int argc, const char * argv[])
{
	NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

	NSDate *checkThisDate = [NSDate dateWithString:@"1969-01-22 05:00:00 +0000"];  // my brithday	
	unsigned long numDays = [[NSDate date] elaspsedDays:checkThisDate];  //get time since 'date'
	
	// Setup formated date
	NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
	[dateFormatter setDateStyle:NSDateFormatterLongStyle];
	[dateFormatter setTimeStyle:NSDateFormatterNoStyle];
	
	// Setup comma formated number
	NSNumberFormatter *numFormatter = [[NSNumberFormatter alloc] init];
	[numFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
	
	// Output
	NSLog(@"It's been %@ days since %@.",
		  [numFormatter stringFromNumber:[NSNumber numberWithUnsignedLong:numDays]],
		  [dateFormatter stringFromDate:checkThisDate]);
	
	[pool drain];
    return 0;
}

Output:
It's been 15,556 days since January 22, 1969.


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wjackman

Newbie

Posts: 12

Re: Chapter 15, Exercise 1 by WTJ

« Reply #3 on: September 02, 2011, 10:50:53 AM »

Hi - Here's my solution. I banged my head on this one for a while, and finally had to look at other peoples' solutions to get the answer - thanks to Bertus and Kevin D. I don't think I would have figured out the date format without help. It still has a problem I couldn't figure out, where I get EXC BAD ACCESS at the [pool drain] line? Perhaps someone could tell me why?

#import <Foundation/Foundation.h>

@interface NSDate (ElapsedDays)

- (unsigned long) elapsedDays: (NSDate *) theDate;

@end

#import "ElapsedDays.h"

@implementation NSDate (ElapsedDays)

- (unsigned long) elapsedDays: (NSDate *) theDate

{
unsigned long res; //set variable to hold result

res = [self timeIntervalSinceDate: theDate]; //result = time between self and test date
return (res/86400); //convert to days
}

@end

#import <Foundation/Foundation.h>
#import "ElapsedDays.h"

int main (int argc, const char * argv[])
{

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

NSDate * testDate = [[NSDate alloc] init]; //date to be tested
NSDate * today = [NSDate date]; //today's date
unsigned long answer;

testDate = [NSDate dateWithString: @"1958-08-26 00:01:00 +0000"]; //set up date to be tested

answer = [today elapsedDays: testDate]; //elapsedDays method

NSLog (@"Elapsed days = %lu", answer);

[testDate release];
[today release];

[pool drain];
return 0;
}

It's been 19365 days since my birthday, a little depressing if you dwell on it too much.


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dpieretti

Newbie

Posts: 11

Re: Chapter 15, Exercise 1

« Reply #4 on: September 02, 2011, 05:19:01 PM »

Here is another solution - this is a good exercise because it requires you to "get your hands dirty" with the NSDate documentation. I also tip my hat to the solutions above. Nice job!

ElapsedDays.h

Code: (Objective-C)

//
//  ElapsedDays.h
//  DateStuff
//
//  Created by Dennis Pieretti on 9/1/11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import <Foundation/Foundation.h>

// Add new NSDate category ElapsedDays
@interface NSDate (ElapsedDays)

-(unsigned long) numberOfElapsedDays: (NSDate *) theDate;

@end

ElapsedDays.m

Code: (Objective-C)

//
//  ElapsedDays.m
//  DateStuff
//
//  Created by Dennis Pieretti on 9/1/11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "ElapsedDays.h"


@implementation NSDate (ElapsedDays)

-(unsigned long) numberOfElapsedDays: (NSDate *) theDate
{
    unsigned long theTimeInSecondsElapsed = [self timeIntervalSinceDate:theDate];
    return theTimeInSecondsElapsed / (24 * 60 * 60);
}

@end

main.m

Code: (Objective-C)

//
//  main.m
//  DateStuff
//
//  Created by Dennis Pieretti on 9/1/11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//
//  Solution to Ch15 #01

#import <Foundation/Foundation.h>
#import "ElapsedDays.h"

int main (int argc, const char * argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
    // set dates to find days between dates  "yyyy-mm-dd hh:mm:ss +GMToffset"
    NSDate *dateOne = [NSDate dateWithString:@"2011-09-09 12:00:00 +0000"];
    NSDate *dateTwo = [NSDate dateWithString:@"2011-09-11 12:00:00 +0000"];
    
    // select a format style for date output from: ShortStyle, MediumStyle, LongStyle, FullStyle 
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init]; 
    [dateFormat setDateStyle:(NSDateFormatterMediumStyle)];
    
    // display the computed days between dates
    NSLog(@"\nThe number of days elapsed from %@ to %@ is %lu", 
          [dateFormat stringFromDate: dateOne], 
          [dateFormat stringFromDate: dateTwo], 
          [dateTwo numberOfElapsedDays: dateOne]);
    
    dateOne = [NSDate dateWithString:@"2011-02-28 12:00:00 +0000"];   
    dateTwo = [NSDate dateWithString:@"2011-03-01 12:00:00 +0000"];
    
    // display the computed days between dates
    NSLog(@"\nThe number of days elapsed from %@ to %@ is %lu",  
          [dateFormat stringFromDate: dateOne], 
          [dateFormat stringFromDate: dateTwo], 
          [dateTwo numberOfElapsedDays: dateOne]);
    
    // test leap year
    dateOne = [NSDate dateWithString:@"2012-02-28 12:00:00 +0000"];   
    dateTwo = [NSDate dateWithString:@"2012-03-01 12:00:00 +0000"];
    
    // display the computed days between dates
    NSLog(@"\nThe number of days elapsed from %@ to %@ is %lu", 
          [dateFormat stringFromDate: dateOne], 
          [dateFormat stringFromDate: dateTwo], 
          [dateTwo numberOfElapsedDays: dateOne]);
    
    // new year
    dateOne = [NSDate dateWithString:@"2012-12-31 12:00:00 +0000"];   
    dateTwo = [NSDate dateWithString:@"2013-01-01 12:00:00 +0000"];
    
    // display the computed days between dates
    NSLog(@"\nThe number of days elapsed from %@ to %@ is %lu",  
          [dateFormat stringFromDate: dateOne], 
          [dateFormat stringFromDate: dateTwo], 
          [dateTwo numberOfElapsedDays: dateOne]);
    
    // one year
    dateOne = [NSDate dateWithString:@"2012-01-01 12:00:00 +0000"];   
    dateTwo = [NSDate dateWithString:@"2012-12-31 12:00:00 +0000"];
    
    // display the computed days between dates
    NSLog(@"\nThe number of days elapsed from %@ to %@ is %lu",  
          [dateFormat stringFromDate: dateOne], 
          [dateFormat stringFromDate: dateTwo], 
          [dateTwo numberOfElapsedDays: dateOne]);
    
    [pool drain];
    return 0;
}

SAMPLE OUTPUT

Code: (Objective-C)

2011-09-02 19:57:25.842 DateStuff[280:903] 
The number of days elapsed from Sep 9, 2011 to Sep 11, 2011 is 2
2011-09-02 19:57:25.844 DateStuff[280:903] 
The number of days elapsed from Feb 28, 2011 to Mar 1, 2011 is 1
2011-09-02 19:57:25.844 DateStuff[280:903] 
The number of days elapsed from Feb 28, 2012 to Mar 1, 2012 is 2
2011-09-02 19:57:25.846 DateStuff[280:903] 
The number of days elapsed from Dec 31, 2012 to Jan 1, 2013 is 1
2011-09-02 19:57:25.846 DateStuff[280:903] 
The number of days elapsed from Jan 1, 2012 to Dec 31, 2012 is 365
Program ended with exit code: 0


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skochan

Administrator
Hero Member

Posts: 3114

Re: Chapter 15, Exercise 1

« Reply #5 on: September 05, 2011, 02:08:40 PM »

Hi, testdate doesn't need to be alloc'ed, as it's created and returned to you by the dateWithString: method (and you lose the reference to original alloc'ed object as a result, which would produce a memory leak). In fact you shouldn't be releasing testate or today, as they're both autoreleased objects created by the NSDate methods.

Cheers,

Steve


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