I'm trying to replace single slash to triple slash in Objective-C. I'm unable to do conversion.
Example:
NSString *string = "pW`-={}|[]456\";
string = [string stringByReplacingOccurrencesOfString:#"\\\" withString:#"\"];
I want to output: pW`-={}|[]456\\
Every back-slash in Objective-C string literal should be presented with two back-slashes (first one is escaping back-slash), otherwise it will not even compile, so
If you want convert this
pW`-={}|[]456\
into this
pW`-={}|[]456\\\
it needs to call
string = [string stringByReplacingOccurrencesOfString:#"\\" withString:#"\\\\\\"];
if vice-versa, then correspondingly
string = [string stringByReplacingOccurrencesOfString:#"\\\\\\" withString:#"\\"];
I have a strange problem encoding my String
For example:
NSString *str = #"\u0e09\u0e31\u0e19\u0e23\u0e31\u0e01\u0e04\u0e38\u0e13";
NSString *utf = [str stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog("utf: %#", utf);
This worked perfectly in log
utf: ฉันรักคุณ
But, when I try using my string that I parsed from JSON with the same string:
//str is string parse from JSON
NSString *str = [spaces stringByReplacingOccurrencesOfString:#"U" withString:#"u"];
NSLog("str: %#, str);
NSString *utf = [str stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog("utf: %#", utf);
This didn't work in log
str: \u0e09\u0e31\u0e19\u0e23\u0e31\u0e01\u0e04\u0e38\u0e13
utf: \u0e09\u0e31\u0e19\u0e23\u0e31\u0e01\u0e04\u0e38\u0e13
I have been finding the answer for hours but still have no clue
Any would be very much appreciated! Thanks!
The string returned by JSON is actually different - it contains escaped backslashes (for each "\" you see when printing out the JSON string, what it actually contains is #"\").
In contrast, your manually created string already consists of "ฉันรักคุณ" from the beginning. You do not insert backslash characters - instead, #"\u0e09" (et. al.) is a single code point.
You could replace this line
NSString *utf = [str stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
with this line
NSString *utf = str;
and your example output would not change. The stringByReplacingPercentEscapesUsingEncoding: refers to a different kind of escaping. See here about percent encoding.
What you need to actually do, is parse the string for string representations of unicode code points. Here is a link to one potential solution: Using Objective C/Cocoa to unescape unicode characters. However, I would advise you to check out the JSON library you are using (if you are using one) - it's likely that they provide some way to handle this for you transparently. E.g. JSONkit does.
Is it possible to make a function that searchs a string for an exact substring so that it will only 'return true' if the exact string if found, not as part of a larger word?
NSString* search = #"tele";
NSString* stringOne = #"telephone";
NSString* stringTwo = #"tele phone";
NSString* stringThree = #"phone tele";
What I mean is: Is it possible to search for a string in a way that the NSString 'search' would be found in strings Two and Three, but not One?
Try using the following function in the NSString class:
- (NSRange)rangeOfString:(NSString *)aString
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/nsstring_Class/Reference/NSString.html
Simplest approach is to append blanks (or whatever your separators are) to front and rear of both strings, then do the search.
I'm looking for a way to make sure a string can be used as a file name under iOS. I'm currently in the section of the code that deletes incompatible characters. I'm wondering if I'm doing it right.
NSString *filename = #"A file name";
fileName = [fileName stringByTrimmingCharactersInSet: [NSCharacterSet controlCharacterSet]];
fileName = [fileName stringByTrimmingCharactersInSet: [NSCharacterSet newlineCharacterSet]];
I'm also wondering if there's already a method that validates a string as a file name.
Thank you for your advice!
Use RegEx:
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"[^a-zA-Z0-9_]+" options:0 error:nil];
filename = [regex stringByReplacingMatchesInString:filename options:0 range:NSMakeRange(0, filename.length) withTemplate:#"-"];
I find this to be cleaner and probably much more performant. This is based on Angel Naydenov's solution, but first constructing Character set with all invalid characters and then calling components(separatedBy:) just once.
Swift 3 & 4
var invalidCharacters = CharacterSet(charactersIn: ":/")
invalidCharacters.formUnion(.newlines)
invalidCharacters.formUnion(.illegalCharacters)
invalidCharacters.formUnion(.controlCharacters)
let newFilename = originalFilename
.components(separatedBy: invalidCharacters)
.joined(separator: "")
Swift 2
let invalidCharacters = NSMutableCharacterSet(charactersInString: ":/")
invalidCharacters.formUnionWithCharacterSet(NSCharacterSet.newlineCharacterSet())
invalidCharacters.formUnionWithCharacterSet(NSCharacterSet.illegalCharacterSet())
invalidCharacters.formUnionWithCharacterSet(NSCharacterSet.controlCharacterSet())
let filename = originalFilename
.componentsSeparatedByCharactersInSet(invalidCharacters)
.joinWithSeparator("")
First of all, you're using the wrong method. Trimming the string will only remove characters in the beginning and the end of the string.
What you're looking for is something more like:
fileName = [fileName stringByReplacingOccurrencesOfString:#"/" withString:#"_"];
However, that's a suboptimal solution, since you'll have to do that for every character you want to exclude, so maybe you want to keep looking or write you're own method for manipulating the string.
iOS is UNIX based and as such I suppose it supports almost any characters in filenames. UNIX allows white spaces, <, >, |, \, :, (, ), &, ;, as well as wildcards such as ? and *, to be quoted or escaped using \ symbol. However I wouldn't use any of those characters in my filenames. In fact, I would restrict the characters in my filenames to 'a'-'z', '0'-'9', '_' and '.'.
As I did not see a list with allowed characters in this question but the question wanted a list with such characters I am adding a bit more details on this topic.
First we need to know what is the file system that iOS devices use. Using multiple online sources this seems to be HFSX which is the HFS+ case sensitive version. And including one link here for reference: https://apple.stackexchange.com/questions/83671/what-filesystem-does-ios-use
Now that we know what the file system is we can look for what characters are not allowed. And these seem to be: colon (:) and slash (/). Here is a link for reference: http://www.comentum.com/File-Systems-HFS-FAT-UFS.html
Having this information and what others have written in this thread my personal preference for removing not allowed characters from file names is the following Swift code:
filename = "-".join(filename.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet()))
filename = "-".join(filename.componentsSeparatedByCharactersInSet(NSCharacterSet.illegalCharacterSet()))
filename = "-".join(filename.componentsSeparatedByCharactersInSet(NSCharacterSet.controlCharacterSet()))
filename = "-".join(filename.componentsSeparatedByString(":"))
filename = "-".join(filename.componentsSeparatedByString("/"))
The reason I am not preferring the RegEx approach is that it seems too restrictive to me. I do not want to restrict my users only to Latin characters. They may as well wish to use some Chinese, Cyrillic or whatever else they like.
Happy coding!
I've had to save remote files locally with filenames containing other characters than basic alpha-numeric characters. I use the method below to strip out potential invalid characters, ensuring it's a valid filename for the filesystem when generating a NSURL using URLWithString:
filename = [[filename componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] componentsJoinedByString:#"" ];
filename = [[filename componentsSeparatedByCharactersInSet:[NSCharacterSet illegalCharacterSet]] componentsJoinedByString:#"" ];
filename = [[filename componentsSeparatedByCharactersInSet:[NSCharacterSet symbolCharacterSet]] componentsJoinedByString:#"" ];
fileURLString = [NSTemporaryDirectory() stringByAppendingPathComponent:filename];
fileURL = [NSURL URLWithString:fileURLString];
You may also want to test for collision errors first using:
[[NSFileManager defaultManager] fileExistsAtPath:[fileURL absoluteString]]
This String extension (Swift 4.2) will help convert an invalid iOS file name to a valid iOS file name.
extension String {
func convertToValidFileName() -> String {
let invalidFileNameCharactersRegex = "[^a-zA-Z0-9_]+"
let fullRange = startIndex..<endIndex
let validName = replacingOccurrences(of: invalidFileNameCharactersRegex,
with: "-",
options: .regularExpression,
range: fullRange)
return validName
}
}
For example
"name.name?/!!23$$#1asd".convertToValudFileName() // "name-name-23-1asd"
"!Hello.312,^%-0//\r\r".convertToValidFileName() // "-Hello-312-0-"
"/foo/bar/pop?soda=yes|please".convertToValidFileName() // "-foo-bar-pop-soda-yes-please"
I'm pretty happy with this solution:
NSString *testString = #"This*is::/legal.😀,?縦書き 123";
NSString *result = [[[testString componentsSeparatedByCharactersInSet:[[NSCharacterSet alphanumericCharacterSet] invertedSet]] filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"length > 0"]] componentsJoinedByString:#"-"];
Output:
"This-is-legal-縦書き-123"
What is this sorcery?
Let me break it up into multiple lines so it's clear what's going on:
NSString *testString = #"This*is::/legal.😀,?縦書き 123";
// Get a character set for everything that's NOT alphanumeric.
NSCharacterSet *nonAlphanumericCharacterSet = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
// Split the string on each non-alphanumeric character, thus removing them.
NSArray *cleanedUpComponentsWithBlanks = [testString componentsSeparatedByCharactersInSet:nonAlphanumericCharacterSet];
// Filter out empty strings ("length" is a KVO-compliant property that the predicate can call on each NSString in the array).
NSArray *cleanedUpComponentsWithoutBlanks = [cleanedUpComponentsWithBlanks filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"length > 0"]];
// Put the components back together and join them with a "-".
NSString *result = [cleanedUpComponentsWithoutBlanks componentsJoinedByString:#"-"];
Enjoy!
Swift 4 Version
Added by john-pang on 2021-09-01 with Swift version:
let testString = "This*is::/legal.😀,?縦書き 123"
// Get a character set for everything that's NOT alphanumeric.
let nonAlphanumericCharacterSet = CharacterSet.alphanumerics.inverted
// Split the string on each non-alphanumeric character, thus removing them.
let cleanedUpComponentsWithBlanks = testString.components(separatedBy: nonAlphanumericCharacterSet)
// Filter out empty strings ("length" is a KVO-compliant property that the predicate can call on each NSString in the array).
let cleanedUpComponentsWithoutBlanks = cleanedUpComponentsWithBlanks.filter { $0.length > 0 }
// Put the components back together and join them with a "-".
let result = cleanedUpComponentsWithoutBlanks.joined(separator: "_")
I came up with the following solution. Works nice so far.
import Foundation
extension String {
func removeUnsupportedCharactersForFileName() -> String {
var cleanString = self
["?", "/", "\\", "*"].forEach {
cleanString = cleanString.replacingOccurrences(of: $0, with: "-")
}
return cleanString
}
}
let a = "***???foo.png"
let validString = a.removeUnsupportedCharactersForFileName()
Base on Marian Answers, here is a string extension to remove any unwanted characters.
extension String {
func stripCharacters() -> String {
var invalidCharacters = CharacterSet(charactersIn: ":/")
invalidCharacters.formUnion(.newlines)
invalidCharacters.formUnion(.illegalCharacters)
invalidCharacters.formUnion(.controlCharacters)
let newString = self
.components(separatedBy: invalidCharacters)
.joined(separator: "_")
return newString
}
}
Example:
let fileName = "Man(lop23/45"
let newFileName = fileName.stripCharacters()
print(newFileName)
Swift 5 extension:
I wanted to remove emojis as well and in windows \ is also an invalid character. So I added symbols charset and backslash \ as well.
extension String {
var validFilename: String {
let invalidCharsets = CharacterSet(charactersIn: ":/\\")
.union(.illegalCharacters)
.union(.controlCharacters)
.union(.symbols)
.union(.newlines)
return self.components(separatedBy: invalidCharsets).joined()
}
}
In Objective-C for iOS, how would I remove the last character of a string using a button action?
In your controller class, create an action method you will hook the button up to in Interface Builder. Inside that method you can trim your string like this:
if ([string length] > 0) {
string = [string substringToIndex:[string length] - 1];
} else {
//no characters to delete... attempting to do so will result in a crash
}
If you want a fancy way of doing this in just one line of code you could write it as:
string = [string substringToIndex:string.length-(string.length>0)];
*Explanation of fancy one-line code snippet:
If there is a character to delete (i.e. the length of the string is greater than 0)
(string.length>0) returns 1 thus making the code return:
string = [string substringToIndex:string.length-1];
If there is NOT a character to delete (i.e. the length of the string is NOT greater than 0)
(string.length>0) returns 0 thus making the code return:
string = [string substringToIndex:string.length-0];
Which prevents crashes.
If it's an NSMutableString (which I would recommend since you're changing it dynamically), you can use:
[myString deleteCharactersInRange:NSMakeRange([myRequestString length]-1, 1)];
The solutions given here actually do not take into account multi-byte Unicode characters ("composed characters"), and could result in invalid Unicode strings.
In fact, the iOS header file which contains the declaration of substringToIndex contains the following comment:
Hint: Use with rangeOfComposedCharacterSequencesForRange: to avoid breaking up composed characters
See how to use rangeOfComposedCharacterSequenceAtIndex: to delete the last character correctly.
The documentation is your friend, NSString supports a call substringWithRange that can shorten the string that you have an return the shortened String. You cannot modify an instance of NSString it is immutable. If you have an NSMutableString is has a method called deleteCharactersInRange that can modify the string in place
...
NSRange r;
r.location = 0;
r.size = [mutable length]-1;
NSString* shorted = [stringValue substringWithRange:r];
...