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to Clock in the Objective-C Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

Implement a clock that handles times without dates.

You should be able to add and subtract minutes to it.

Two clocks that represent the same time should be equal to each other.

Setup

There are two different methods of getting set up to run the tests with Objective-C:

  • Create an Xcode project with a test target which will run the tests.
  • Use the ruby gem objc as a test runner utility.

Both are described in more detail here: http://exercism.io/languages/objective-c

Submitting Exercises

When submitting an exercise, make sure your solution file is in the same directory as the test code.

The submit command will look something like:

exercism submit <path-to-exercism-workspace>/objective-c/clock/Clock.m

You can find the Exercism workspace by running exercism debug and looking for the line beginning with Workspace.

Source

Pairing session with Erin Drummond https://twitter.com/ebdrummond

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

ClockTest.m

#import <XCTest/XCTest.h>

#if __has_include("ClockExample.h")
# import "ClockExample.h"
# else
# import "Clock.h"
#endif

@interface ClockTest : XCTestCase

@end

@implementation ClockTest //!OCLint

#pragma mark - Create: Test creating a new clock with an initial time.

- (void)testOnTheHour {
    XCTAssertEqualObjects(@"08:00", [[Clock clockWithHours:8] description]);
}

- (void)testPastTheHour {
    XCTAssertEqualObjects(@"11:09", [[Clock clockWithHours:11 minutes:9] description]);
}

- (void)testMidnightIsZeroHours {
    XCTAssertEqualObjects(@"00:00", [[Clock clockWithHours:24] description]);
}

- (void)testHourRollsOver {
    XCTAssertEqualObjects(@"01:00", [[Clock clockWithHours:25] description]);
}

- (void)testHourRollsOverContinuously {
    XCTAssertEqualObjects(@"04:00", [[Clock clockWithHours:100] description]);
}

- (void)testSixtyMinutesIsNextHour {
    XCTAssertEqualObjects(@"02:00", [[Clock clockWithHours:1 minutes:60] description]);
}

- (void)testMinutesRollOver {
    XCTAssertEqualObjects(@"02:40", [[Clock clockWithHours:0 minutes:160] description]);
}

- (void)testMinutesRollOverContinuously {
    XCTAssertEqualObjects(@"04:43", [[Clock clockWithHours:0 minutes:1723] description]);
}

- (void)testHoursAndMinutesRollOver {
    XCTAssertEqualObjects(@"11:01", [[Clock clockWithHours:201 minutes:3001] description]);
}

- (void)testHoursAndMinutesRollOverToExactlyMidnight {
    XCTAssertEqualObjects(@"00:00", [[Clock clockWithHours:72 minutes:8640] description]);
}

- (void)testNegativeHour {
    XCTAssertEqualObjects(@"23:15", [[Clock clockWithHours:-1 minutes:15] description]);
}

- (void)testNegativeHourRollsOver {
    XCTAssertEqualObjects(@"23:00", [[Clock clockWithHours:-25] description]);
}

- (void)testNegativeHourRollsOverContinuously {
    XCTAssertEqualObjects(@"05:00", [[Clock clockWithHours:-91] description]);
}

- (void)testNegativeMinutes {
    XCTAssertEqualObjects(@"00:20", [[Clock clockWithHours:1 minutes:-40] description]);
}

- (void)testNegativeMinutesRollOver {
    XCTAssertEqualObjects(@"22:20", [[Clock clockWithHours:1 minutes:-160] description]);
}

- (void)testNegativeMinutesRollOverContinuously {
    XCTAssertEqualObjects(@"16:40", [[Clock clockWithHours:1 minutes:-4820] description]);
}

- (void)testNegativeHoursAndMinutesBothRollOverContinuously {
    XCTAssertEqualObjects(@"22:10", [[Clock clockWithHours:-121 minutes:-5810] description]);
}

//#pragma mark - Add: Test adding and subtracting minutes.

- (void)testAddMinutes {
    Clock *clock = [[Clock clockWithHours:10] addMinutes:3];
    XCTAssertEqualObjects(@"10:03", clock.description);
}

- (void)testAddNoMinutes {
    Clock *clock = [[Clock clockWithHours:6 minutes:41] addMinutes:0];
    XCTAssertEqualObjects(@"06:41", clock.description);
}

- (void)testAddToNextHour {
    Clock *clock = [[Clock clockWithHours:0 minutes:45] addMinutes:40];
    XCTAssertEqualObjects(@"01:25", clock.description);
}

- (void)testAddMoreThanOneHour {
    Clock *clock = [[Clock clockWithHours:10] addMinutes:61];
    XCTAssertEqualObjects(@"11:01", clock.description);
}

- (void)testAddMoreThanTwoHoursWithCarry {
    Clock *clock = [[Clock clockWithHours:0 minutes:45] addMinutes:160];
    XCTAssertEqualObjects(@"03:25", clock.description);
}

- (void)testAddAcrossMidnight {
    Clock *clock = [[Clock clockWithHours:23 minutes:59] addMinutes:2];
    XCTAssertEqualObjects(@"00:01", clock.description);
}

- (void)testAddMoreThanOneDay {
    // (1500 min = 25 hrs)
    Clock *clock = [[Clock clockWithHours:5 minutes:32] addMinutes:1500];
    XCTAssertEqualObjects(@"06:32", clock.description);
}

- (void)testAddMoreThanTwoDays {
    Clock *clock = [[Clock clockWithHours:1 minutes:1] addMinutes:3500];
    XCTAssertEqualObjects(@"11:21", clock.description);
}

- (void)testSubtractMinutes {
    Clock *clock = [[Clock clockWithHours:10 minutes:3] subtractMinutes:3];
    XCTAssertEqualObjects(@"10:00", clock.description);
}

- (void)testSubtractToPreviousHour {
    Clock *clock = [[Clock clockWithHours:10 minutes:3] subtractMinutes:30];
    XCTAssertEqualObjects(@"09:33", clock.description);
}

- (void)testSubtractMoreThanAnHour {
    Clock *clock = [[Clock clockWithHours:10 minutes:3] subtractMinutes:70];
    XCTAssertEqualObjects(@"08:53", clock.description);
}

- (void)testSubtractAcrossMidnight {
    Clock *clock = [[Clock clockWithHours:0 minutes:3] subtractMinutes:4];
    XCTAssertEqualObjects(@"23:59", clock.description);
}

- (void)testSubtractMoreThanTwoHours {
    Clock *clock = [[Clock clockWithHours:0 minutes:0] subtractMinutes:160];
    XCTAssertEqualObjects(@"21:20", clock.description);
}

- (void)testSubtractMoreTHanTwoHoursWithBorrow {
    Clock *clock = [[Clock clockWithHours:6 minutes:15] subtractMinutes:160];
    XCTAssertEqualObjects(@"03:35", clock.description);
}

- (void)testSubtractMoreThanOneDay {
    // (1500 min = 25 hrs)
    Clock *clock = [[Clock clockWithHours:5 minutes:32] subtractMinutes:1500];
    XCTAssertEqualObjects(@"04:32", clock.description);
}

- (void)testSubtractMoreThanTwoDays {
    Clock *clock = [[Clock clockWithHours:2 minutes:20] subtractMinutes:3000];
    XCTAssertEqualObjects(@"00:20", clock.description);
}

//#pragma mark - Equal: Construct two separate clocks, set times, test if they are equal.

- (void)testClocksWithSameTime {
    Clock *clock1 = [Clock clockWithHours:15 minutes:37];
    Clock *clock2 = [Clock clockWithHours:15 minutes:37];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksAMinuteApart {
    Clock *clock1 = [Clock clockWithHours:15 minutes:36];
    Clock *clock2 = [Clock clockWithHours:15 minutes:37];
    XCTAssertNotEqual(clock1, clock2);
}

- (void)testClocksAnHourApart {
    Clock *clock1 = [Clock clockWithHours:14 minutes:37];
    Clock *clock2 = [Clock clockWithHours:15 minutes:37];
    XCTAssertNotEqual(clock1, clock2);
}

- (void)testClocksWithHourOverflow {
    Clock *clock1 = [Clock clockWithHours:10 minutes:37];
    Clock *clock2 = [Clock clockWithHours:34 minutes:37];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithHourOverflowBySeveralDays {
    Clock *clock1 = [Clock clockWithHours:3 minutes:11];
    Clock *clock2 = [Clock clockWithHours:99 minutes:11];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeHour {
    Clock *clock1 = [Clock clockWithHours:22 minutes:40];
    Clock *clock2 = [Clock clockWithHours:-2 minutes:40];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeHourThatWraps {
    Clock *clock1 = [Clock clockWithHours:17 minutes:3];
    Clock *clock2 = [Clock clockWithHours:-31 minutes:3];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeHourThatWrapsMultipleTimes {
    Clock *clock1 = [Clock clockWithHours:13 minutes:49];
    Clock *clock2 = [Clock clockWithHours:-83 minutes:49];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithMinuteOverflow {
    Clock *clock1 = [Clock clockWithHours:0 minutes:1];
    Clock *clock2 = [Clock clockWithHours:0 minutes:1441];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithMinuteOverflowBySeveralDays {
    Clock *clock1 = [Clock clockWithHours:2 minutes:2];
    Clock *clock2 = [Clock clockWithHours:2 minutes:4322];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeMinute {
    Clock *clock1 = [Clock clockWithHours:2 minutes:40];
    Clock *clock2 = [Clock clockWithHours:3 minutes:-20];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeMinuteThatWraps {
    Clock *clock1 = [Clock clockWithHours:4 minutes:10];
    Clock *clock2 = [Clock clockWithHours:5 minutes:-1490];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeMinuteThatWrapsMultipleTimes {
    Clock *clock1 = [Clock clockWithHours:6 minutes:15];
    Clock *clock2 = [Clock clockWithHours:6 minutes:-4305];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeHoursAndMinutes {
    Clock *clock1 = [Clock clockWithHours:7 minutes:32];
    Clock *clock2 = [Clock clockWithHours:-12 minutes:-268];
    XCTAssertEqualObjects(clock1, clock2);
}

- (void)testClocksWithNegativeHoursAndMinutesThatWrap {
    Clock *clock1 = [Clock clockWithHours:18 minutes:7];
    Clock *clock2 = [Clock clockWithHours:-54 minutes:-11513];
    XCTAssertEqualObjects(clock1, clock2);
}

@end
//
//  Clock.m
//  Clock
//
//  Created by Steve Huey on 6/10/17.
//  Copyright © 2017 Steve Huey. All rights reserved.
//

#import "Clock.h"

#define kHoursPerDay 24
#define kMinutesPerHour 60

NSInteger mod(NSInteger a, NSInteger N)
{
   if (a >= 0)
   {
      return a % N;
   }
   else
   {
      // http://math.stackexchange.com/a/519853
      NSInteger output = a;
      
      while (output < 0)
      {
         output += N;
      }
      
      return output;
   }
}

NSInteger minutesToHours(NSInteger minutes)
{
   return (NSInteger)floor((double)minutes / (double)kMinutesPerHour);
}

@interface Clock ()
@property (nonatomic, assign) NSInteger hours;
@property (nonatomic, assign) NSInteger minutes;
@end

@implementation Clock
+ (instancetype)clockWithHours:(NSInteger)hours
{
   return [[self class] clockWithHours:hours minutes:0];
}

+ (instancetype)clockWithHours:(NSInteger)hours minutes:(NSInteger)minutes
{
   Clock* clock = [[Clock alloc] init];
   
   clock.hours = mod((hours + minutesToHours(minutes)), kHoursPerDay);
   clock.minutes = mod(minutes, kMinutesPerHour);
   
   return clock;
}

- (NSString *)description
{
   return [NSString stringWithFormat:@"%02ld:%02ld",
           (long)self.hours, (long)self.minutes];
}

- (BOOL)isEqual:(id)object
{
   BOOL result = NO;
   
   if ([object isKindOfClass:[Clock class]])
   {
      Clock* otherClock = (Clock*)object;
      
      result = [[self description] isEqualToString:[otherClock description]];
   }
   
   return result;
}

- (Clock*)addMinutes:(NSInteger)minutes
{
   return [[self class] clockWithHours:self.hours
                               minutes:self.minutes + minutes];
}

- (Clock*)subtractMinutes:(NSInteger)minutes
{
   return [self addMinutes:-minutes];
}
@end

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