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copied!<p>First off, your line:</p> <pre><code>NSString *firstLetter = [codeString substringFromIndex:1]; </code></pre> <p>does not get the first letter. This gives you a new string the contains all of the original string EXCEPT the first character. This is the opposite of what you want. You want:</p> <pre><code>NSString *firstLetter = [codeString substringToIndex:1]; </code></pre> <p>But there is a better way to see if the first character is a letter or not.</p> <pre><code>unichar firstChar = [[codeString uppercaseString] characterAtIndex:0]; if (firstChar >= 'A' && char <= 'Z') { // The first character is a letter from A-Z or a-z } </code></pre> <p>However, since iOS apps deal with international users, it is far from ideal to simply look for the character being in the letters A-Z. A better approach would be:</p> <pre><code>unichar firstChar = [codeString characterAtIndex:0]; NSCharacterSet *letters = [NSCharacterSet letterCharacterSet]; if ([letters characterIsMember:firstChar]) { // The first character is a letter in some alphabet } </code></pre> <p>There are a few cases where this doesn't work as expected. <code>unichar</code> only holds 16-bit characters. But <code>NSString</code> values can actually have some 32-bit characters in them. Examples include many Emoji characters. So it's possible this code can give a false positive. Ideally you would want to do this:</p> <pre><code>NSRange first = [codeString rangeOfComposedCharacterSequenceAtIndex:0]; NSRange match = [codeString rangeOfCharacterFromSet:[NSCharacterSet letterCharacterSet] options:0 range:first]; if (match.location != NSNotFound) { // codeString starts with a letter } </code></pre>

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