• Origin story: iOS was created and developed by Apple Inc in 2007. It is the world's second-most widely used mobile operating system after Android. The iOS App Store started in 2008 with an initial of 500 apps available. According to BuildFire, there are about 2.2 million apps available for download on the iOS app store,1 million of which are native for iPads.
• Widely popular: iOS holds about 25% of the market share after Android, which holds 68%, and the rest are smaller operating systems.
• Built using different programming languages: Swift is the most-used language to build an iOS app. Some other languages are Objective-C, C#, Python, C++, and HTML 5.
• Other trivia: The name "iOS" and its logo impose standards to limit the use of the iOS trademark to "non-certified" devices outside of their ecosystem.

• Good revenue: According to StatCounter, Apple users spend more money on app-purchases as compared to Android.
• Requires limited effort on design: iOS powers Apple devices only, which makes it easier for developers to design apps that have to fit the limited number of screens and devices. Unlike Android, which has various screen sizes.

Here are some of the tools used by iOS developers:

1. IDEs and Code Editors

Integrated Development Environments provide all the components that are necessary for product building. The most popular tools under this category for iOS are:

• XCode - Made by Apple, reduces development time with intuitive features.
• CodeRunner - This tool has great compilation abilities and is full of amazing features.

2. App Design

The following tools are commonly used to make iOS apps that are visually appealing and provide a great, simple experience:

• Flawless - this is a free tool that can be used with XCode and allows for design comparison and analysis.
• Figma - a more complex design app that is browser-based, and compatible with most modern browsers.

3. Debugging

RayGun is a commonly used debugging tool in iOS development. It is a premium tool that shows users how people interact with the iOS app built.

4. Testing

XCTest and XCTestUI are used for this purpose. These are automation frameworks made by Apple and are a part of the XCode editor.

5. Plugins

These are some of the commonly used add-on plugins that enhance the iOS app building process:

• GitDiff - this adds visual data to XCode so that it's easy to identify and track the changes made to the code.
• Dash - comprehensive documentation and cheat sheets are available on this tool, allowing for easy reference and building.
• Injections - this tool adds, or injects, new code in your application code files to speed up the development process.

Below are some key points that we at Flexiple have learned through trial and error - a process of filtering through over 15,000 developers. You can use these in your process to hire iOS developers.

• Years of software development experience: Be specific about the technology you’re looking for and the number of years of experience needed. A proxy to years of experience can be the number of production-level apps worked on.
• Expertise in a specific programming language: Different programming languages used to develop an iOS app have its own nuances. While a good programmer can pick up other languages, it’s a plus point to hire a developer who already has expertise in it.
• Type of products built in the past: Based on the type of product you are trying to build - social network, SAAS product, etc. - you can prioritize certain developers over others.
• Exposure to specific industries: Developers who have built products in certain industries will already know key aspects of laying the foundation for a great product and will be able to predict possible problems.
• Experience working remotely: A developer with past remote work experience is an added advantage as they would have first-hand experience of everything - right from how contracts work to streamlined communication, as well as timelines and deliverables.
• Strong communication: An essential thing to look at when hiring a freelancer is excellent communication skills. Since all the interaction happens online, a freelancer should be able to effectively communicate to ensure a streamlined execution of all work.

You can check out a more detailed job description for iOS developers here.

Now that you have made a quality JD, it can still be tricky to evaluate the skills of your applicants when you hire iOS developers. To help you with that, we have created a pool of questions that a good iOS developer should be comfortable with.

It is important to note that the ability to answer these questions doesn't imply that you have a top quality candidate. But it definitely is a big step in that direction.

To help you navigate through these questions, we’ve categorized the interview questions in 3 parts:

A. Basic concepts: Includes all basic concepts used across languages but we've focused on their significance in iOS. This will give you an understanding of how strong their programming foundation is.

B. Advanced concepts: Includes all concepts that someone with higher expertise should know.

C. DS/Algorithm questions: To test the logical capability of the candidate.

A. Basic concepts

Coming soon!

B. Advanced concepts

Coming soon!

C. Data Structure/ Algorithm

1. Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Note that an empty string is also considered valid.

class ValidParenthesesFunc {
    func isValid(_ s: String) -> Bool {
        var stc = [Character]()

        for char in s {
            if char == "(" || char == "[" || char == "{" {
                stc.append(char)
            } else if char == ")" {
                guard stc.count != 0 && stc.removeLast() == "(" else {
                    return false
                }
            } else if char == "]" {
                guard stc.count != 0 && stc.removeLast() == "[" else {
                    return false
                }
            } else if char == "}" {
                guard stc.count != 0 && stc.removeLast() == "{" else {
                    return false
                }
            }
        }
        return stc.isEmpty
    }
}

The above code will input 0(false). 

2. What will the output of the following code be?

$x = 10;
$y = 5;
$z = 3;
if ($x / $y / $z)
    print "hi";
else
    print "hello";

The answer is A because the floating-point division returns a non zero value = 0.66 which evaluates 
to true and outputs ‘hi’.

3. What will the output of the following code be?

$x = 2
$y = 4
$z = 6
if($z > $y > $x) {
    echo “true”;
}else{
    echo “false”;
}

The answer is False. It may look like the output can be true because 6 > 4 > 2 is true, but PHP evaluates $z > $y 
first, which returns a boolean value of 1 or true. This value (true or 1) is compared
to the next integer in the chain, bool(1) > $z, which will result in NULL and echo “false.”

That’s it! You’re all set to hire a freelance iOS developer. As discussed, it isn't easy to find a quality freelance iOS developer but this guide makes the process easier for you. To offload the entire hiring process, reach out to us at Flexiple . We've designed a high-quality, 6-step screening process to find the top 1%, freelance developers. You can find the best freelance iOS developers here. We've already served over a hundred clients, earning great reviews for the quality of service.

Lastly, to quickly summarize the process of hiring iOS developers for you:

• Note your project requirements and hire accordingly. Do not go for the lowest or the highest-paid developer.
• Don’t hire without vetting- consider asking questions right from the basics to advanced to logical problems.
• Look for companies like Flexiple that help you find the perfect fit.

That is everything you need to know if you want to hire iOS developers. Happy hiring! :)