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to Space Age in the Objective-C Track

Published at Apr 22 2019 · 0 comments
Test suite

Given an age in seconds, calculate how old someone would be on:

  • Earth: orbital period 365.25 Earth days, or 31557600 seconds
  • Mercury: orbital period 0.2408467 Earth years
  • Venus: orbital period 0.61519726 Earth years
  • Mars: orbital period 1.8808158 Earth years
  • Jupiter: orbital period 11.862615 Earth years
  • Saturn: orbital period 29.447498 Earth years
  • Uranus: orbital period 84.016846 Earth years
  • Neptune: orbital period 164.79132 Earth years

So if you were told someone were 1,000,000,000 seconds old, you should be able to say that they're 31.69 Earth-years old.

If you're wondering why Pluto didn't make the cut, go watch this youtube video.


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/space-age/SpaceAge.m

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


Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=01

Submitting Incomplete Solutions

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


#import <XCTest/XCTest.h>

#if __has_include("SpaceAgeExample.h")
# import "SpaceAgeExample.h"
# else
# import "SpaceAge.h"


@interface SpaceAgeTest : XCTestCase


@implementation SpaceAgeTest

static const double AgeAccuracy = 0.01;

- (void)testAgeInSeconds {
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:1000000];
    XCTAssertEqual(1000000, age.seconds);

- (void)testAgeInEarthYears { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:1000000000];
    XCTAssertEqualWithAccuracy(31.69, age.onEarth, AgeAccuracy);

- (void)testAgeInMercuryYears { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:2134835688];
    XCTAssertEqualWithAccuracy(67.65, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(280.88, age.onMercury, AgeAccuracy);

- (void)testAgeInVenusYears { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:189839836];
    XCTAssertEqualWithAccuracy(6.02, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(9.78, age.onVenus, AgeAccuracy);

- (void)testAgeOnMars { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:2329871239];
    XCTAssertEqualWithAccuracy(73.83, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(39.25, age.onMars, AgeAccuracy);

- (void)testAgeOnJupiter { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:901876382];
    XCTAssertEqualWithAccuracy(28.58, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(2.41, age.onJupiter, AgeAccuracy);

- (void)testAgeOnSaturn { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:3000000000];
    XCTAssertEqualWithAccuracy(95.06, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(3.23, age.onSaturn, AgeAccuracy);

- (void)testAgeOnUranus { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:3210123456];
    XCTAssertEqualWithAccuracy(101.72, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(1.21, age.onUranus, AgeAccuracy);

- (void)testAgeOnNeptune { //!OCLINT
    SpaceAge *age = [[SpaceAge alloc] initWithSeconds:8210123456];
    XCTAssertEqualWithAccuracy(260.16, age.onEarth, AgeAccuracy);
    XCTAssertEqualWithAccuracy(1.58, age.onNeptune, AgeAccuracy);



#import "SpaceAge.h"

@implementation SpaceAge
- (id) initWithSeconds: (long) seconds {
    self = [super init];
    _seconds = seconds;
    _onEarth = seconds / 31557600.0;
    _onMercury = _onEarth / 0.2408467;
    _onVenus = _onEarth / 0.61519726;
    _onMars = _onEarth / 1.8808158;
    _onJupiter = _onEarth / 11.862615;
    _onSaturn = _onEarth / 29.447498;
    _onUranus = _onEarth / 84.016846;
    _onNeptune = _onEarth / 164.79132;
    return self;


#import <Foundation/Foundation.h>


@interface SpaceAge : NSObject
@property long seconds;
@property double onEarth;
@property double onMercury;
@property double onVenus;
@property double onMars;
@property double onJupiter;
@property double onSaturn;
@property double onUranus;
@property double onNeptune;

- (id) initWithSeconds: (long) seconds;


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