Swift Program to Get Input from the User

Getting input from the user in Swift is very easy with the help of the readLine() function. This function returns a string of characters which is read from the standard input at the end of the current line. If the control is already reached the EOF when the readLine() function is called then this method will return nil.

Syntax

Following is the syntax of Swift readLine() function ?

<span class="pln">readLine</span><span class="pun">(</span><span class="pln">strippingNewline</span><span class="pun">:</span><span class="pln"> </span><span class="kwd">true</span><span class="pun">)</span><span class="pln">
</span><span class="typ">Or</span><span class="pln"> 
readLine</span><span class="pun">()</span>

Reading integer

Example

The following program shows how to get input from the user.

<div class="code-mirror  language-swift" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token keyword">import</span> <span class="token class-name">Foundation</span>
<span class="token keyword">import</span> <span class="token class-name">Glibc</span>

<span class="token function">print</span><span class="token punctuation">(</span><span class="token string-literal"><span class="token string">"Please enter number 1"</span></span><span class="token punctuation">)</span>
<span class="token keyword">var</span> num1 <span class="token operator">=</span> <span class="token class-name">Int</span><span class="token punctuation">(</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">!</span><span class="token punctuation">)</span><span class="token operator">!</span>
<span class="token function">print</span><span class="token punctuation">(</span><span class="token string-literal"><span class="token string">"Please enter number 2"</span></span><span class="token punctuation">)</span>
<span class="token keyword">var</span> num2 <span class="token operator">=</span> <span class="token class-name">Int</span><span class="token punctuation">(</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">!</span><span class="token punctuation">)</span><span class="token operator">!</span>

<span class="token keyword">var</span> sum <span class="token operator">=</span> num1 <span class="token operator">+</span> num2
<span class="token function">print</span><span class="token punctuation">(</span><span class="token string-literal"><span class="token string">"The sum of </span><span class="token interpolation-punctuation punctuation">\(</span><span class="token interpolation">num1</span><span class="token interpolation-punctuation punctuation">)</span><span class="token string"> and </span><span class="token interpolation-punctuation punctuation">\(</span><span class="token interpolation">num2</span><span class="token interpolation-punctuation punctuation">)</span><span class="token string"> is </span><span class="token interpolation-punctuation punctuation">\(</span><span class="token interpolation">sum</span><span class="token interpolation-punctuation punctuation">)</span><span class="token string">"</span></span><span class="token punctuation">)</span>
</div>

Input

<span class="typ">Please</span><span class="pln"> enter number </span><span class="lit">1</span><span class="pln">
</span><span class="lit">10</span><span class="pln">
</span><span class="typ">Please</span><span class="pln"> enter number </span><span class="lit">2</span><span class="pln">
</span><span class="lit">20</span>

Output

The sum of 10 and 20 is 30

Here in the above code, we take two integer type inputs from the user with the help of the readLine() function. As we knew that the readLine() function returns a string so we use Int() function to convert the string into integer as shown in the below code ?

var num1 = Int(readLine()!)!

Display the sum of the given numbers that is 10 + 20 = 30.

Reading String

Example

The following program shows how to get input from the user.

<div class="code-mirror  language-swift" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token keyword">import</span> <span class="token class-name">Foundation</span>
<span class="token keyword">import</span> <span class="token class-name">Glibc</span>

<span class="token function">print</span><span class="token punctuation">(</span><span class="token string-literal"><span class="token string">"Please enter your favourite subject: "</span></span><span class="token punctuation">)</span>
<span class="token keyword">if</span> <span class="token keyword">let</span> inputData <span class="token operator">=</span> <span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
   <span class="token function">print</span><span class="token punctuation">(</span><span class="token string-literal"><span class="token string">"Subject is </span><span class="token interpolation-punctuation punctuation">\(</span><span class="token interpolation">inputData</span><span class="token interpolation-punctuation punctuation">)</span><span class="token string">!"</span></span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>
</div>

STDIN Input

<span class="typ">Please</span><span class="pln"> enter your favourite subject</span><span class="pun">:</span><span class="pln"> 
C</span><span class="pun">++</span>

Output

Subject is C++!

Here in the above code, user entered his/her favourite subject using the readLine() function. And display the entered subject using the below code ?

<span class="kwd">if</span><span class="pln"> </span><span class="kwd">let</span><span class="pln"> inputData </span><span class="pun">=</span><span class="pln"> readLine</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
   </span><span class="kwd">print</span><span class="pun">(</span><span class="str">"Subject is \(inputData)!"</span><span class="pun">)</span><span class="pln">
</span><span class="pun">}</span>

Where the inputData variable stores the value of readLine() function and display the output that is "Subject is C++!".