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Can anyone please explain the difference between this
[display setText:[[display text] stringByAppendingString:digit ]];
and this
[display setText:digit];
The code is rather clear. But if you don't understand:
Here [display setText:[[display text] stringByAppendingString:digit ]]; a new digit will be added to the digits currently displaying on the screen. This BOOL value userIsInTheMiddleOfTypingANumber is extremely straightforward - it is said that there are always digits on the screen and a new digit must be added to them. This method stringByAppendingString returns a new string made by appending a given digit to the currently displayed digits in the UITextField.
And here [display setText:digit]; all the text which are displayed in the UITextField will be overwritten with a new digit value. But as I suppose it is used when there are no digits on the screen and we need to write the first one.I don't know what is using for displaying digits in that app. But if it is UITextField then using setText is a bad idea - it is a deprecated method. You should use text property instead.
This is an extremely simple code which you need to understand yourself. So my advice you to read some introductory books on CocoaTouch and iOS with simple examples there are plenty of them: http://www.amazon.com/Beginning-iOS-Development-Exploring-SDK/dp/1430245123/ref=pd_sim_b_8 . And don't forget to use official documentation.
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I'm using Ruby 2.4. I have a string with letters and numbers, something like
str = "123abc234abb"
How do I find all the letters occurring after the last number in the string? For example, if I applied the function to the above, it would yield
abb
You could use a positive lookbehind:
"123abc234abb"[/(?<=\d)?[a-zA-Z]+\z/]
#=> "abb"
Try this
str.rpartition(/\d+/).last
How does this work?
rpartition splits the string into three parts, using reverse matching
last picks the post-match part from the three results
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Are there any methods for taking a string and converting all lowercase letters to uppercase?
I was thinking of making a for-loop to run through, check each character, see if it is in range 0061-007A (lowercase letters) and just subtracting 26 (base 16) (converts to the uppercase counterpart) from the unicode code and adding that character back to the string.
But I figured I'd check if there is a simpler method already out there... googled but couldn't find anything... I'm sure I could use a 1x1 UIWebView and load some javascript (that does this) with my string into the UIWebView but there has got to be something already in Objective-C other than the manual approach I first mentioned right?
You do not need a loop - you can use either
NSString *upper = [src uppercaseString];
or
NSString *upper = [src uppercaseStringWithLocale:myLocale];
for targeting a specific locale.
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I am creating a check to make sure the user remembers to enter the house number as well as road number in the address.
how would I go about checking to see if a NSString contains 0-9 number characters?
This could be as simple as using rangeOfCharacterFromSet:
NSCharacterSet * set = [NSCharacterSet characterSetWithCharactersInString:#"0123456789"];
if ([aString rangeOfCharacterFromSet:set].location != NSNotFound) {
NSLog(#"This string contains illegal characters");
}
You could also give a look at regular expressions, if you would like to do something fancier with your validation, but in order to just check if a string contains any number, the above is enough.
Have a look at -[NSString (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)aSet]
and +[NSCharacterSet (id)decimalDigitCharacterSet].
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Once I use [NSString hash] and get a NSUInteger, is there any way I can use that NSUInteger and turn it back into the original NSString? Apple doesn't really say anything about the implementation of the hash method in the docs.
FYI: I'm trying to store identifierForVendor as a NSNumber (specifically in either the major or minor property of a CLBeacon).
No. The hash is 32 or 64 bits, a string can be much longer, so it is inherently lossy, and the hash values are not unique (the same hash corresponds to multiple strings).
Actually, hash is not supposed to be de-coded. You may want to read something like http://en.wikipedia.org/wiki/Hash_function
Apple says "If two string objects are equal (as determined by the isEqualToString: method), they must have the same hash value". That's all you can get.
If you want to store it for later comparisons, then you should hash the both NSStrings & compare the resulting NSUIntegers
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I am working on a calculator App.
The NSMutablestring is used for calculation E.g "5-3*8-(-1)/77".
But the label can't display endless an NSMutablestring, so is there have any way to limit NSMutablestring's length?
(not too long, I want the NSMutablestring's length to be less than 100).
You can get the first 100 characters of a string as follows:
NSString *first100chars = [myString substringToIndex:100];
However, it sounds like you need to prevent the user from actually entering a string this long, which is a different problem. The comments to your question give examples of other people asking similar questions (e.g. Set the maximum character length of a UITextField), I suggest you check those.
This is a job for an NSFormatter subclass. That's exactly what it's for.