I am trying to make a utility method for FMDB which will take an NSArray of values and return a string of placeholders for use in an IN statement based on the number of values in the array.
I can't think of an elegant way of creating this string, am I missing some NSString utility method:
// The contents of the input aren't important.
NSArray *input = #[#(55), #(33), #(12)];
// Seems clumsy way to do things:
NSInteger size = [input count];
NSMutableArray *placeholderArray = [[NSMutableArray alloc] initWithCapacity:size];
for (NSInteger i = 0; i < size; i++) {
[placeholderArray addObject:#"?"];
}
NSString *output = [placeholderArray componentsJoinedByString:#","];
// Would return #"?,?,?" to be used with input
What about this?
NSArray *input = #[#(55), #(33), #(12)];
NSUInteger count = [input count];
NSString *output = [#"" stringByPaddingToLength:(2*count-1) withString:#"?," startingAtIndex:0];
// Result: ?,?,?
stringByPaddingToLength fills the given string (the empty string in this case)
to the given length by appending characters from the pattern #"?,".
Related
I'm trying to use NSData to pull information out of a text file, and then load it into a dictionary.
First I create a string of the text file, and load each record into an array.
Then I break apart the each record into individual data elements.
The problem I'm having is that when the dictionary is fully populated, I then use addObject to load it into the array, which it does do successfully. The problem is that when the next loop creates a new dictionary, the same dictionary gets loaded into the array, and I end up an array of all the same dictionaries, instead of multiple different dictionary objects.
I'm guessing there is some simple mistake I'm making that is causing this error. Any help would be appreciated.
NSString *clientListFile = [NSURL URLWithString: #"/textfile"];
NSData *clientListDataFile = [NSData dataWithContentsOfFile:clientListFile];
NSString *clientListString = [[NSString alloc]initWithBytes:[clientListDataFile bytes] length:[clientListDataFile length] encoding:NSUTF8StringEncoding];
NSString *returnDelimiter = #"\n";
NSString *commaDelimiter = #",";
NSString *exclamationDelimiter = #"!";
NSArray *keysAndObjects = [[NSArray alloc]init];
NSMutableDictionary *clientList = [[NSMutableDictionary alloc]init];
NSMutableArray *clientListOfDictionaries = [[NSMutableArray alloc]init];
NSArray *sentenceArray = [clientListString componentsSeparatedByString:returnDelimiter];
for (int i = 0; i < [sentenceArray count]; i=i+1) {
[clientList removeAllObjects]; //to start with a fresh dictionary for the next iteration
NSString *recordSentence = [sentenceArray objectAtIndex:i];
NSArray *attributes = [recordSentence componentsSeparatedByString:commaDelimiter];
for (int j = 0; j < [attributes count]; j = j+1) {
NSString *pairsOfItems = [attributes objectAtIndex:j];
//a small arry, of only two objects, the first is the key, the second is the object
keysAndObjects = [pairsOfItems componentsSeparatedByString:exclamationDelimiter];
[clientList setObject:[keysAndObjects lastObject] forKey:[keysAndObjects firstObject]];
}
[clientListOfDictionaries addObject:clientList];
}
When I used NSLog to see what's in the dictionary, I mulitple objects of the same dictionary repeated, even though up earlier in the iteration, I can see that the code is creating separate and unique dictionaries.
Instead of this line
[clientListOfDictionaries addObject:clientList];
you can have
[clientListOfDictionaries addObject:[[NSArray alloc] initWithArray:clientList];
That way you will be adding new arrays to clientListOfDictionaries instead of the same one.
Move this line:
NSMutableDictionary *clientList = [[NSMutableDictionary alloc]init];
to just after the first for loop line and then delete the line:
[clientList removeAllObjects];
It's important to create a new dictionary for each iteration.
You should also delete the following line:
NSArray *keysAndObjects = [[NSArray alloc]init];
and change:
keysAndObjects = [pairsOfItems componentsSeparatedByString:exclamationDelimiter];
to:
NSArray *keysAndObjects = [pairsOfItems componentsSeparatedByString:exclamationDelimiter];
You are allocated and initialising your clientList dictionary outside of the for loop, so you only have one dictionary, which you are storing in your array multiple times. Adding the dictionary to the array does not copy it, it merely adds a pointer to the object.
you need to move
NSMutableDictionary *clientList = [[NSMutableDictionary alloc]init];
inside your first for loop in place of
[clientList removeAllObjects];
Also, componentsSeparatedByString: returns an NSArray, so you don't need to allocate and initialise one. You can simply define the variable -
NSArray *keysAndObjects;
Because you're using the same clientList variable for each iteration of the loop. You need to create a whole new dictionary object each time.
Try this modified code:
NSData *clientListDataFile = [NSData dataWithContentsOfFile:clientListFile];
NSString *clientListString = [[NSString alloc]initWithBytes:[clientListDataFile bytes] length:[clientListDataFile length] encoding:NSUTF8StringEncoding];
NSString *returnDelimiter = #"\n";
NSString *commaDelimiter = #",";
NSString *exclamationDelimiter = #"!";
NSArray *keysAndObjects = nil;
NSMutableArray *clientListOfDictionaries = [[NSMutableArray alloc] init];
NSArray *sentenceArray = [clientListString componentsSeparatedByString:returnDelimiter];
for (NSUInteger i = 0; i < [sentenceArray count]; ++i) {
NSMutableDictionary *clientList = [[NSMutableDictionary alloc] init]; //to start with a fresh dictionary for the next iteration
NSString *recordSentence = [sentenceArray objectAtIndex:i];
NSArray *attributes = [recordSentence componentsSeparatedByString:commaDelimiter];
for (NSUInteger j = 0; j < [attributes count]; ++j) {
NSString *pairsOfItems = [attributes objectAtIndex:j];
//a small arry, of only two objects, the first is the key, the second is the object
keysAndObjects = [pairsOfItems componentsSeparatedByString:exclamationDelimiter];
[clientList setObject:[keysAndObjects lastObject] forKey:[keysAndObjects firstObject]];
}
[clientListOfDictionaries addObject:clientList];
}
An alternate option, though likely less efficient, is to to change the line:
[clientListOfDictionaries addObject:clientList];
to
[clientListOfDictionaries addObject:[clientList copy]];
That lets you keep using the same clientList variable, since you're adding a copy of it to the clientListOfDictionaries array. I just point that out because it might help you understand what's going on.
Also, note that I changed this line for you:
NSArray *keysAndObjects = [[NSArray alloc]init];
to
NSArray *keysAndObjects = nil;
Because it's just a pointer that is set by your call to componentsSeparatedByString, you don't need to allocate an array for it. That array will just vanish in your first iteration of the loop.
Should be added the new dictionary to array. Otherwise it will not add to an array. Every object in array have same dictionary mapping. So it will give you the same dictionary value. Create new dictionary for every object and add to array.
for (int i = 0; i < [sentenceArray count]; i=i+1) {
NSMutableDictionary *clientList = [[NSMutableDictionary alloc]init];
NSString *recordSentence = [sentenceArray objectAtIndex:i];
NSArray *attributes = [recordSentence componentsSeparatedByString:commaDelimiter];
for (int j = 0; j < [attributes count]; j = j+1) {
NSString *pairsOfItems = [attributes objectAtIndex:j];
//a small arry, of only two objects, the first is the key, the second is the object
NSArray *keysAndObjects = [pairsOfItems componentsSeparatedByString:exclamationDelimiter];
[clientList setObject:[keysAndObjects lastObject] forKey:[keysAndObjects firstObject]];
}
[clientListOfDictionaries addObject:clientList];
}
I am creating a word scrambler and I am having issues randomizing the letters. When the letters get randomized, it doesn't make sense.
For example, the word PARK shows as AAPA. So, as you can tell it won't make sense for the user when it is time to unscramble.
Just so you know, I am using a .plist file to hold the words.
This is the code I am using to randomize the letters:
_words = [NSMutableArray arrayWithCapacity:scramblelength];
for (int i=0;i<scramblelength;i++) {
NSString *letter = [scramble substringWithRange:[scramble rangeOfComposedCharacterSequenceAtIndex:arc4random()%[scramble length]]];
Then, I am creating UIImageViews to display the scrambled words:
if (![letter isEqualToString:#""]) {
GameView *boxes = [[GameView alloc] initWithLetter:letter andSideLength:boxSide];
boxes.center = CGPointMake(xOffset + i*(boxSide + kTileMargin), kScreenHeight/4*3);
[self.scrambleView addSubview:boxes];
[_words addObject:boxes];
What am I doing wrong here? I would like for the letters in the scrambled words to make sense.
Please help, I am stuck on this one!
Thanks!
As long as your string length will fit in 32 bits, this should be fine. If not, I would replace arc4random_uniform with a uniform random number generator in C++ and compile this as an Objective-C++ module.
The code simply iterates through the string, and swaps each composed character sequence with some random composed character sequence from the same string.
Sorry, that's what happens when you are arrogant and just type out code. Let me know if you have trouble with this one...
For much larger strings, there is a more efficient way, but this seems to do the trick.
NSMutableString category...
#interface NSMutableString (Scramble)
- (void)scramble;
#end
#implementation NSMutableString (Scramble)
static void
swapRanges(NSMutableString *string, NSRange iRange, NSRange jRange)
{
// Need to replace the "trailing" component first
if (NSEqualRanges(iRange, jRange)) return;
if (iRange.location > jRange.location) {
NSRange tmpRange = iRange;
iRange = jRange;
jRange = tmpRange;
}
NSString *iString = [self substringWithRange:iRange];
NSString *jString = [self substringWithRange:jRange];
[string replaceCharactersInRange:jRange withString:iString];
[string replaceCharactersInRange:iRange withString:jString];
}
- (void)scramble
{
for (NSUInteger i = 0; i < self.length; ++i) {
NSRange iRange = [self rangeOfComposedCharacterSequenceAtIndex:i];
NSUInteger j = arc4random_uniform(self.length);
NSRange jRange = [self rangeOfComposedCharacterSequenceAtIndex:j];
swapRanges(self, iRange, jRange);
}
}
#end
NSString category...
#interface NSString (Scramble)
- (NSString*)scrambledString;
#end
#implementation NSString (Scramble)
- (NSString *)scrambledString
{
NSMutableString *result = [self mutableCopy];
[result scramble];
return [result copy];
}
#end
Sample use...
[someMutableString scramble];
NSString *mixedUp = [someString scrambledString];
Or, if you are comfortable with C++, convert to a std::wstring, call std::random_shuffle, then convert that to a NSString. Lots less bugs when using proven, well tested code.
When you are getting a random letter, you need to do something to remove that letter from your NSMutableArray (ie the word's letters when in order). So as you iterate through the word, each time there are fewer characters remaining. Right now, from your limited code block (the first one), it appears you might not be doing that. You want something like "[_words removeObjectAtIndex:letterIndex]" and you would also want to iterate from number of letters down to zero as you remove items from the array also: for (int i=[_words count]; i > [_words count]; i--) because you need to go from 4 letters down to 0 letters left.
So, I'm sure there are more efficient ways to do this, but I go by the rule of not optimizing until you need to. With that in mind, this code appears to work correctly:
- (NSString *)scrambleWord:(NSString *)word {
NSMutableArray *letterArray = [self letterArrayFromWord:word];
NSMutableString *returnValue = [[NSMutableString alloc] init];
do {
int randomIndex = arc4random() % letterArray.count;
[returnValue appendString:letterArray[randomIndex]];
[letterArray removeObjectAtIndex:randomIndex];
if (letterArray.count == 1) {
[returnValue appendString:letterArray[0]];
break;
}
} while (YES);
if ([[returnValue copy] isEqualToString:word]) {
return [self scrambleWord:word];
} else {
return [returnValue copy];
}
}
- (NSMutableArray *)letterArrayFromWord:(NSString *)word {
NSMutableArray *array = [NSMutableArray array];
for (int i = 0; i < word.length; i = i + 1) {
[array addObject:[NSString stringWithFormat:#"%C", [word characterAtIndex:i]]];
}
return array;
}
I have been struggling with this question for couple days now. Really need your help and opinion.
We have a string, that holds a text:
NSString *contentOfFile = [[NSString alloc] initWithString:#"This is string#1"];
Now I have to log symbols, that were met in this string without duplicates. Result should look like this:
whitespace symbol here
#
1
g
h
i
n
r
s
t
I know that this is solved very simple in C code using char set and iterators but I am looking for the same simple and elegant way of handling this operation in objective-c.
I was thinking of using NSCharacterSet on the string somehow but I have a lack of knowledge in objective-c so I need your help guys please. Thanks in advance to everyone who replies.
Take advantage of a trait of NSSet: Its members are distinct.
NSString *contentOfFile = #"This is string#1";
NSMutableSet *set = [NSMutableSet set];
NSUInteger length = [contentOfFile length];
for (NSUInteger index = 0; index < length; index++)
{
NSString *substring = [contentOfFile substringWithRange:NSMakeRange(index, 1)];
[set addObject:substring];
}
NSLog(#"%#", set);
However, there's one remaining problem, and that is the members of a set are also unordered. Fortunately, arrays are ordered. So if you change the last line:
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"self" ascending:YES];
NSArray *array = [set sortedArrayUsingDescriptors:#[sortDescriptor]];
NSLog(#"%#", array);
If case insensitivity is important to you, there unfortunately is no 'case-insensitive' option for NSSet. However, you could convert your source string to all lowercase, like this:
NSString *contentOfFile = [#"This is string#1" lowercaseString];
and this would give you results exactly matching your sample output.
// Create the string
NSString *contentOfFile = #"This is string#1";
// Remove all whitespaces
NSString *whitespaceRemoval = [contentOfFile stringByReplacingOccurrencesOfString:#" " withString:#""];
// Initialize an array to store the characters
NSMutableArray *components = [NSMutableArray array];
// Iterate through the characters and add them to the array
for (int i = 0; i < [whitespaceRemoval length]; i++) {
NSString *character = [NSString stringWithFormat:#"%c", [whitespaceRemoval characterAtIndex:i]];
if (![components containsObject:character]) {
[components addObject:character];
}
}
I have several NSStrings which I add to an NSArray. The string may contain special characters. In the end I want to print the array to a UILabel.
The very simplified code (if you think I missed something, let me know):
NSString *strBuffer = #"Röckdöts";
NSLog(#"String: %#", strBuffer);
NSMutableArray *marrSelectedStrings = [[NSMutableArray alloc] init];
[marrSelectedStrings addObject:strBuffer];
NSLog(#"Array: %#", marrSelectedStrings);
NSUInteger iCount = [marrSelectedStrings count]
for (NSUInteger i = 0; i < iCount; i++)
{
NSLog(#"element %d: %#", i, [marrSelectedStrings objectAtIndex: i]);
}
In a different UIViewController:
self.label.text = [NSString stringWithFormat:#"%#", marrSelectedStrings];
The string itself prints out fine. For the array however, it depends on the output method, whether the console diplays the correct special character or code for it. The label only prints code instead of the real characters. The print out via NSLog looks like the following:
Buffer: Röckdöts
Array: (
R\U00f6ckd\U00f6ts
)
element 0: Röckdöts
Whereas the label reads:
R\U00f6ckd\U00f6ts
I tried using stringWithUTF8String during the adding to the array as well as encoding during assigning it to the label like so, but it didn't change the result:
// adding with UTF8 encoding
[marrSelectedStrings addObject:[NSString stringWithUTF8String:[strBuffer UTF8String]]];
// printing to label with UTF8 encoding
self.label.text = [NSString stringWithUTF8String:[[NSString stringWithFormat:#"%#", marrSelectedStrings] UTF8String]];
Is there an easier way to simply print the array with correct character encoding to the UILabel than iterating over the array and appending every single word?
Try this
NSString * result = [[marrSelectedStrings valueForKey:#"description"] componentsJoinedByString:#""];
self.label.text = result;
try like this
NSMutableArray *marrSelectedStrings = [[NSMutableArray alloc] init];
[marrSelectedStrings addObject:strBuffer];
NSString *description = [marrSelectedStrings description];
if (description) {
const char *descriptionChar = [description cStringUsingEncoding:NSASCIIStringEncoding];
if (descriptionChar) {
NSString *prettyDescription = [NSString stringWithCString:descriptionChar encoding:NSNonLossyASCIIStringEncoding];
if (prettyDescription) {
description = prettyDescription;
}
}
}
NSLog(#"Array: %#", description);
I would like to create a string based on the number of characters passed in. Each character passed in will be a "X". So for example, if the length passed in is 5, then the string created should be
NSString *testString=#"XXXXX";
if it is 2 then it would be
NSString *testString=#"XX";
Can anyone tell me what the most efficient way to do this would be?
Thank you!
If you know the maximum length is some reasonable number then you could do something simple like this:
- (NSString *)xString:(NSUInteger)length {
static NSString *xs = #"XXXXXXXXXXXXXXXXXXXXXXXXXXX";
return [xs substringToIndex:length];
}
NSString *str = [self xString:5]; // str will be #"XXXXX";
If you pass in too large of a length, the app will crash - add more Xs to xs.
This approach is more efficient than building up an NSMutableString but it does make an assumption about the maximum length you might need.
- (NSString *)stringOf:(NSString *)str times:(NSInteger)count
{
NSMutableString *targ = [[NSMutableString alloc] initWithCapacity:count];
for (int i=0; i < count; i++)
{
[targ appendString:str];
}
return targ;
}
and
[self stringOf:#"X" times:4];
note that initWithCapacity: (in performance manner) better than init. But I guess that's all for efficiency.
The way I would do it is
NSMutableString *xString = [[NSMutableString alloc] init];
while ( int i = 0; i < testString.length; i++ ) {
[xString appendString:#"X"];
i++;
}
NSUInteger aLength. // assume this is the argument
NSMutableString *xStr = [NSMutableString stringWithCapacity: aLength];
for ( NSUInteger i = 0; i < aLength; i++ ) {
[xStr appendFormat:#"X"];
}
The following will do what you ask in one call:
NSString *result = [#"" stringByPaddingToLength:numberOfCharsWanted
withString:characterToRepeat
startingAtIndex:0];
where numberOfCharsWanted is an NSUInteger and characterToRepeat is an NSString containing the character.