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to Reverse String in the Objective-C Track

Published at Dec 19 2020 · 0 comments
Test suite

Reverse a string.

For example: input: "cool" output: "looc"


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/robot-name/RobotName.m

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


A debugging session with Paul Blackwell at gSchool. http://gschool.it

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("ReverseStringExample.h")
# import "ReverseStringExample.h"
# else
# import "ReverseString.h"

@interface ReverseStringTest : XCTestCase


@implementation ReverseStringTest

-(void)testReverseEmptyString {
    NSString *inputString = [NSString string];
    NSString *expectedOutput = [NSString string];
    XCTAssertEqualObjects(expectedOutput, [inputString reverseString]);

-(void)testReverseWord {
    NSString *inputString = @"robot";
    NSString *expectedOutput = @"tobor";
    XCTAssertEqualObjects(expectedOutput,[inputString reverseString]);

-(void)testReverseCapitalisedWord {
    NSString *inputString = @"Ramen";
    NSString *expectedOutput = @"nemaR";
    XCTAssertEqualObjects(expectedOutput, [inputString reverseString]);

-(void)testReverseSentenceWithPunctuation {
    NSString *inputString = @"I'm hungry!";
    NSString *expectedOutput = @"!yrgnuh m'I";
    XCTAssertEqualObjects(expectedOutput, [inputString reverseString]);

-(void)testReversePalindrome {
    NSString *inputString = @"racecar";
    NSString *expectedOutput = @"racecar";
    XCTAssertEqualObjects(expectedOutput, [inputString reverseString]);


ReverseString/ReverseString Tests/ReverseString.h

//  ReverseString.h
//  ReverseString
//  Created by Nadiar Syaripul on 19/12/20.

#import <Foundation/Foundation.h>


@interface NSString (ReverseString)

- (NSString *)reverseString;



ReverseString/ReverseString Tests/ReverseString.m

//  ReverseString.m
//  ReverseString
//  Created by Nadiar Syaripul on 19/12/20.

#import "ReverseString.h"

@implementation NSString (ReverseString)

- (NSString *)reverseString {
    NSMutableString *reversed = [NSMutableString string];
    int length = (int)[self length];
    for (int i=length; i>0; i--) {
        NSString *nextString = [self substringWithRange:NSMakeRange(i-1, 1)];
        [reversed appendString:nextString];
    return reversed;


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