I have a variable name referencing question for the Objective C gurus out there.
Lets say I have 6 UILabels on a form, the are setup with properties naming them myLabel1 - myLabel6
I would like to go through a for loop and populate these with something depending on the loop but im unsure how to specifiy the for loops variable and make it part of the labels name.
Here is what I would like to do:
for (int LP = 0; i <5)
{
labelLP.text = [NSString stringWithFormat:#"My label number:%d", LP};
}
What im not sure of is how to reference the label and append the LP int and use it in my loop. I'm sure there is a way to do this just not sure how.. Anyone??
you can always take advantage of the dynamic runtime of objective-c:
id var = object_getIvar(self,class_getInstanceVariable([self class], [[NSString stringWithFormat:#"label%d",LP] UTF8String]));
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html
Whether one likes this approach is a question of style, but here's a way that should work:
for (int LP = 1; i <=6)
{
NSString *labelName = [NSString stringWithFormat: #"label%d", i];
UILabel *labelLP = (UILabel*)[self valueForKey: labelName];
labelLP.text = [NSString stringWithFormat:#"My label number:%d", LP};
}
I don't think you can create variable names on the fly, at least not trivially.
You could always use a switch case inside your loop:
for (int i=0; i<5; i++) {
switch(i) {
case 1:
myLabel1.text = [NSString stringWithFormat:#"My label number: %d", i];
break;
case 2:
myLabel2.text = [NSString stringWithFormat:#"My label number: %d", i];
break;
...
...
}
}
You could also store your labels in an array, and loop through that array.
The important point is not to get fixated about the variable names, but to think about why you need your objects and how to get them.
Related
Here's my program so far. My intention is to have it so the if statement compares the letter in the string letterGuessed to a character in the string userInputPhraseString. Here's what I have. While coding in xCode, I get an "expected '['"error. I have no idea why.
NSString *letterGuessed = userInputGuessedLetter.text;
NSString *userInputPhraseString = userInputPhraseString.text;
int loopCounter = 0;
int stringLength = userInputPhraseString.length;
while (loopCounter < stringLength){
if (guessedLetter isEqualToString:[userInputPhraseString characterAtIndex:loopIndexTwo])
{
//if statement true
}
loopCounter++;
}
You are missing enclosing square brackets on this line:
if (guessedLetter isEqualToString:[userInputPhraseString characterAtIndex:loopIndexTwo])
It should be:
if ([guessedLetter isEqualToString:[userInputPhraseString characterAtIndex:loopIndexTwo]])
Edit that won’t fix your problem, though, because characterAtIndex: returns a unichar, not an NSString.
It's not clear what you are trying to do.. But I suppose that letterGuessed has one character... And that userInputPhraseString has many characters. So you want to know if letterGuessed is inside userInputPhraseString correct?
This is one solution without loops involved.. I replaced the input with fixed values for testing and tested the code.. It works.
NSString *letterGuessed = #"A"; //Change to your inputs
NSString *userInputPhraseString = #"BBBA"; //Since it has A it will be true in the test
NSCharacterSet *cset = [NSCharacterSet characterSetWithCharactersInString:letterGuessed];
NSRange range = [userInputPhraseString rangeOfCharacterFromSet:cset];
if (range.location != NSNotFound) { //Does letterGuessed is in UserInputPhraseString?
NSLog(#"YES"); //userInput Does contain A...
} else {
NSLog(#"NO");
}
In regards to your code... I fixed a couple of errors, first you are trying to get a UniChar (Integer) value for the character and want to compare it to a NSString which is an Object. Also fixed a couple of issues with syntax you had and used the right approach which is to return a range of characters. Again for doing what you want to accomplish the example above is the best approach I know, but for the sake of learning, here is your code fixed.
NSString *letterGuessed = #"A"; //Change to your inputs
NSString *userInputPhraseString = #"BBBA"; //Since it has A it will be true in the test
NSInteger loopCounter = 0; //Use NSInteger instead of int.
NSInteger stringLength = userInputPhraseString.length;
BOOL foundChar = NO; //Just for the sake of returning NOT FOUND in NSLOG
while (loopCounter < stringLength){
//Here we will get a letter for each iteration.
NSString *scannedLetter = [userInputPhraseString substringWithRange:NSMakeRange(loopCounter, 1)]; // Removed loopCounterTwo
if ([scannedLetter isEqualToString:letterGuessed])
{
NSLog(#"FOUND CHARACTER");
foundChar = YES;
}
loopCounter++;
}
if (!foundChar) NSLog(#"NOT FOUND");
NSRange holds the position, length.. So we move to a new position on every iteration and then get 1 character.
Also if this approach is what you want, I would strongly suggest a for-loop.
I am very new to Objective-C with Cocoa, and I need help.
I have a for statement in which I loop i from 1 to 18, and I would like to add an object to an NSMutableArray in this loop. Right now I have:
chapterList = [[NSMutableArray alloc] initWithCapacity:18];
for (int i = 1; i<19; i++)
{
[chapterList addObject:#"Chapter"+ i];
}
I would like it to add the objects, chapter 1, chapter 2, chapter 3... , chapter 18. I have no idea how to do this, or even if it is possible. Is there a better way? Please Help
Thanks in advance,
chapterList = [[NSMutableArray alloc] initWithCapacity:18];
for (int i = 1; i<19; i++)
{
[chapterList addObject:[NSString stringWithFormat:#"Chapter %d",i]];
}
good luck
Try:
[chapterList addObject:[NSString stringWithFormat:#"Chapter %d", i]];
In Objective-C/Cocoa you can't append to a string using the + operator. You either have to use things like stringWithFormat: to build the complete string that you want, or things like stringByAppendingString: to append data to an existing string. The NSString reference might be a useful place to start.
If you're wanting strings that merely say Chapter 1, Chapter 2, you can just do this:
chapterList = [[NSMutableArray alloc] initWithCapacity:18];
for (int i = 1; i<19; i++) {
[chapterList addObject:[NSString stringWithFormat:#"Chapter %d",i]];
}
And don't forget to release the array when you're done, as you're calling alloc on it.
I'm not sure if I worded the subject correctly. I am looping through an array, within each loop I am trying to instantiate a class, but I want to dynamically create the name. Like so:
int i = 0;
for(NSString* thisdatarow in filedata) {
i++;
NSString* thisad = [NSString stringWithFormat:#"ad%d", i];
NSLog(#"%#", thisad);
AdData* thisad = [AdData new];
}
In the example above I want AdData* thisad... to be named dynamically - "ad1", "ad2", "ad3"...and so on. I get a conflicting type error.
This code also generated an error:
int i = 0;
for(NSString* thisdatarow in filedata) {
i++;
AdData* [NSString stringWithFormat:#"ad%d", i] = [AdData new];
}
Is there a way to do this?
You can't do that in Objective-C.
Use a NSString to AdData map--it'll do basically the same thing!
**edit: To clarify, use an:
NSMutableDictionary *dict;
with keys that are NSString* objects containing the ad names, and values that are the AdData* objects.
i.e.
[dict setValue:ad1 forKey:#"ad1"];
to set the values, and
[dict valueForKey:#"ad1"];
to get the values. (ignore the obvious memory leaks there with the strings...)
This isn't possible. While Objective-C is very dynamic, it's not that dynamic.
The suggested way to do this would be to create your instances and put them into an array, not assigning them to explicitly named variables.
You can then refer to them individually using their index in the array.
Something like this:
NSMutableArray *ads = [NSMutableArray array];
for(NSString* thisdatarow in filedata) {
AdData* thisad = [[[AdData alloc] init] autorelease];
[ads addObject:thisad];
}
// get third ad:
AdData *ad = [ads objectAtIndex:2];
Alternatively you could create an NSDictionary, if you really want to refer to them by a name, like this:
NSMutableDictionary *ads = [NSMutableDictionary dictionary];
int i = 0;
for(NSString* thisdatarow in filedata) {
i++;
AdData* thisad = [[[AdData alloc] init] autorelease];
NSString *keyName = [NSString stringWithFormat:#"ad%d", i];
[ads setObject:thisad forKey:keyName];
}
// get third ad
AdData *ad = [ads objectForKey:#"ad2"];
Cant be done Without using a C array, which would look like this:
AdData **ad = malloc(sizeof(AdData) * numberOfAds);
ad[1] = [AdData new];
// etc.
if (ad)
free(ad);
But I don't know how that would work because of how Objective-C classes are stored....
Local variable names are a purely compile-time concept. So you cannot do anything "dynamic" (i.e. at runtime) with it. The compiler is free to rename the variables and add or remove variables as it sees fit.
If you think about it, what is the point of dynamically manipulating local variable names? In order to use the dynamically-named variable again, you must either 1) explicitly refer to the variable name, in which case you have hard-coded the name (not so dynamic), or 2) dynamically construct the name again. If it's (1), then there is only a fixed set of variable names, so dynamic-ness is unnecessary. If it's (2), you're missing the point of local variable names (the whole point of which is so they can be referred to explicitly).
sorry for the simple question but how do you make a CAlayers using a for loop?
I have this now but what is the proper way of doing this?
for (int n = 1; n <= 6; n++) {
NSString *theCloud = [NSString stringWithFormat:#"cloudImage%d",n];
NSString *theCloudLayer = [NSString stringWithFormat:#"cloudLayer%d",n];
CALayer *theCloudLayer = theCloud.layer;
}
any help is appreciated.
Use an NSArray or NSMutableArray, not a bunch of variables with numbers at the end of their names (also known as a Poor Man's Array).
So that would be something like:
NSArray *cloudImages; // Use this to store your objects currently in the cloudLayerN variables
NSMutableArray *cloudLayers = [NSMutableArray array];
for (id cloud in cloudImages) {
[cloudLayers addObject:[cloud layer]];
}
I need to pick string valur from an NSMutableArray then save it into a plist. I've builded an NSMutableArray to display infos in table View. Maximum allowed index is 8. (paste just two in example)
The problem if the String doesn't exist, I get the following error:
sDict is a dictionary for saving datas to a property list file.
the code:
- (IBAction)save:(id)sender {
(...)
NSString *One;
NSString *Two;
...etc
if ([self.smOne objectAtIndex:0])
One = [self.smOne objectAtIndex:0];
if ([self.smOne objectAtIndex:1])
Two = [self.smOne objectAtIndex:1];
...etc
if (One)
[sDict setObject:[self.smTwo objectAtIndex:0]
forKey:[UserM stringByAppendingString:One]];
[sDict setObject:[self.smThree objectAtIndex:0]
forKey:[UserS stringByAppendingString:One]];
[sDict setObject:[self.smFour objectAtIndex:0]
forKey:[UserP stringByAppendingString:One]];
if (Two)
[sDict setObject:[self.smTwo objectAtIndex:1]
forKey:[UserM stringByAppendingString:Two]];
[sDict setObject:[self.smThree objectAtIndex:1]
forKey:[UserS stringByAppendingString:Two]];
[sDict setObject:[self.smFour objectAtIndex:1]
forKey:[UserParM stringByAppendingString:Two]];
...etc
}
This code works if all objects are present, but fails if it miss one of the object at index.
I really don't know how to check properly if the object is present or not, cause code above seem's to don't works well.
I've tried with [self.smOne count] but as problem to pass as a Int or String to make conditions with.
Thanks for answer.
it looks like you're explicitly checking smOne from indices 1 through 8. But you also mentioned that the array can have up to 8. So if it's missing, say, 6, 7 and 8, you'd still be calling [smOne objectAtIndex:6], which would result in an NSRangeException being raised as 6 is out of bounds for the array.
try this instead:
int i = 0;
for ( NSString *aString in self.smOne )
{
[sDict setObject:[self.smTwo objectAtIndex:i]
forKey:[UserM stringByAppendingSting:aString]];
[sDict setObject:[self.smThree objectAtIndex:i]
forKey:[UserS stringByAppendingString:aString]];
[sDict setObject:[self.smFour objectAtIndex:i]
forKey:[UserP stringByAppendingString:aString]];
i++;
}
it'll go through each object in the smOne array and add the object into sDict regardless of how many items you have in smOne.
also, be careful with how you're generating your keys. there's the possibility that [UserM stringByAppendingSting:aString] won't always be unique.
Sorry to ask again but i have dificulties to find how to rebuild arrays from the key/string couple saved with the loop.
i've tried this:
int i = 0;
for (NSString *SMServ in [temp objectForKey:
[UserMen stringByAppendingFormat:#"%d",i]]){
NSString *SMMem[i];
SMMem[i] = [temp objectForKey:[UserMen stringByAppendingFormat:#"%d",i]];
NSArray *theArray = [ NSArray arrayWithObjects:SMMem count:i];
i++;
}
But nothing happens.
if i try with for (i = 0; i < 9; i ++) and (i + 1) instead of [i], i get same bounds errors in the first example.
thanks again for help.
Well, finally it ,works. Thanks for link to the documentation, i read too fast last time.
I'm sure this is not the cleanest way, but it works with this loop:
for (key in sDict) {
if ([sDict valueForKey:[UserMen stringByAppendingFormat:#"%d",i]]) {
tempMe = [sDict valueForKey:[UserMen stringByAppendingFormat:#"%d",i]];
if (tempMe) {
[manArray insertObject:tempMe atIndex:(0 + a)];
[bankArray insertObject:[NSString stringWithFormat:#"%d",i] atIndex:(0 + a)];
a++;
}
}
if ([sDict valueForKey:[UserSerial stringByAppendingFormat:#"%d",i]]) {
SMSer = [sDict valueForKey:[UserSerial stringByAppendingFormat:#"%d",i]];
if (SMSer) {
[serArray insertObject:SMSer atIndex:(0 + b)];
b++;
}
}
if ([sDict valueForKey:[UserPart stringByAppendingFormat:#"%d",i]]) {
SMPart = [sDict valueForKey:[UserPart stringByAppendingFormat:#"%d",i]];
if (SMPart) {
[partArray insertObject:SMPart atIndex:(0 + c)];
c++;
}
}
i++;
}