I like to combine multiple lines of code into one, when I can. Example:
int64_t siz = [self getFileSizeAsInt64_t: filePath];
NSString * str = [self convLongLongToCommaStr: siz];
return( str );
becomes
return [self convLongLongToCommaStr: [self getFileSizeAsInt64_t: filePath]];
Here is an example of a three-line code pattern I see in my code a lot that I'd like to combine into one line. But, I've not been able to do it and I'm not sure if it is even possible.
UIImageView * imgView = ctlObjs[iImgIdx];
[imgView setImage: nextImage];
ctlObjs[iImgIdx] = imgView;
Thanks for any insights on how to do this, if it is possible.
As Yar points out, that third line is not necessary. But you could combine the first two like so:
[ctlObjs[iImgIdx] setImage:nextImage];
Or, if ctlObjs is a NSArray or NSMutableArray, you might want the following, which makes the intent clear and offers better code completion:
[(UIImageView *) ctlObjs[iImgIdx] setImage:nextImage];
Having said that, the fact that you can combine multiple lines of code into one doesn't mean that you necessarily should. IMHO, code legibility is probably more important than compactness. I personally would stick with:
UIImageView *imgView = ctlObjs[iImgIdx];
[imgView setImage: nextImage];
Just
[ctlObjs[iImgIdx] setImage:nextImage];
Related
I have to create a number of UIImageViews based on values stored in an NSString. The value that is stored will become the name for my UIImageView, each one will be created individually of course.
So to keep things simple my question is, can one create a UIImageView based on the value stored within an NSString?
Rough Example:
-(UIImageView)createMyFruitViews:(NSString *)fruit
{
NSString *fruit = #"";
UIImageView *fruitImage [fruit value]; //<-- made up for example purposes.
return fruitImage;
}
If this is not possible, could you please suggest a way around this?
FYI I've read through the forums too, the only thing that comes close is How to use NSSstring to instantiate a UIImageview; however I don't understand the answer and I am not sure that it can apply to what I need.
Try using UIImageView *fruitImage = [[UIImageView alloc] initWithImage:[UIImage imageNamed:fruit]];
I'm not quite sure I understood what you need... as far as I can tell, you have the name of an image on a NSString object, right?
Lets say you have an array of strings, each string representing the name of an image:
NSArray *myImageNames = [NSArray arrayWithObjects:#"image1.png", #"image2.png", #"image3.png", nil];
Then you'll create your imageViews using these images:
for (NSString *imageName in myImageNames) {
UIImageView *myImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:imageName]];
[self.view addSubview:myImageView];
[myImageView release]; // If you're not using ARC
}
If I didn't get exactly what you need, please let me know.
I have a UISegmentedControl with several segments, each with a different "title". I want to be able to read in a NSString, and programmatically select the segment whose title matches that string. Say I start with something like:
NSString *stringToMatch = #"foo";
UISegmentedControl *seg = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObjects:#"foo",#"bar",#"baz", nil]];
I want to do something like:
[seg selectSegmentWithTitle:stringToMatch];
But since there is no method called selectSegmentWithTitle, this doesn't work. Is anyone aware of a method that would be similar to this though?
I've also thought of looping over all the titles in seg, similar to this:
int i = 0;
for (UISegment *thisSeg in [seg allSegmentsInOrder])
{
if ([thisSeg.title isEqualToString:stringToMatch])
{
[seg setSelectedSegmentIndex:i];
break;
}
i++;
}
but to my knowledge there is no such thing as UISegment, nor is there a method allSegmentsInOrder. Again, does anyone know of any changes I could make to get this to work?
Thirdly, I could probably subclass UISegmentedControl to somehow add the methods I want it to have. I hate subclassing like that though, cause I'd have to go and re-declare all my segments and other inconvenient things like that. But it may be the only way to go...
Perhaps the way to do this is totally different from the three ideas I listed above. I'm open to whatever.
So while I was typing this question up, I kept searching and realized that my second method from OP is pretty close. I figured I should still post what I came up with, in case someone else is looks for something like this in the future.
for (int i = 0; i < [seg numberOfSegments]; i++)
{
if ([[seg titleForSegmentAtIndex:i] isEqualToString:stringToMatch])
{
[seg setSelectedSegmentIndex:i];
break;
}
//else {Do Nothing - these are not the droi, err, segment we are looking for}
}
if ([seg selectedSegmentIndex] == -1)
{
NSLog(#"Error - segment with title %# not found in seg",stringToMatch);
NSLog(#"Go back and fix your code, you forgot something");
// prob should do other stuff here to let the user know something went wrong
}
This still feels a little hacky, and is probably against some best practice guide somewhere, but if there's a finite list of titles and you can be certain stringToMatch will always be on that list, I'm thinking it should be fine.
I'm new to Objective-C so sorry if this is a newbie question.
I've searched for a couple of hours and can't seem to find an answer to my question.
So I'm trying to access a UIImageView so I can hide/unhide it by concatenating strings together to get the name of the UIImageView which should hide/unhide.
I have it working by doing:
self.faceItemEyesFrightened.hidden = false;
However the Frightened part of the name could be different each time a button is clicked so, trying to refactor my code I run a function which returns the type of UIImageView should be affected.
So I have the following:
NSString *fullEmotionString = [#"faceItemEyes" stringByAppendingString:emotionIs];
where emotionIs would be Frightened, therefore forming
faceItemEyesFrightened
So my problem comes when I wish to do something like this:
self.fullEmotionString.hidden = false;
Obviously that's not the right way of doing it but I'm not sure how it should be done, any advice greatly appreciated.
Cheers!
You could use NSSelectorFromString like this:
SEL selector = NSSelectorFromString(fullEmotionString);
UIImageView *imageView = [self performSelector:selector];
imageView.hidden = NO;
Note, that this requires a getter called faceItemEyesFrightened to be defined, which is usually this case if you're using properties and didn't change the name of the accessors.
That being said, I think this is not an optimal solution to your problem.
You could for instance subclass UIImageView and add an enum MyImageViewEmotion that describes the emotion in the image. Then, instead of using lots of variables, like faceItemEyesFrightened or faceItemEyesHappy, you could put all of them in a simple array and then get one of them like this:
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"self.emotion == %ld",
MyImageViewEmotionFrightened];
MyImageView *imageView = [eyeImageViews filteredArrayUsingPredicate:predicate][0]
Of use an NSDictionary, where you put the emotion string as the key and the image views as the value. Then you could access them very easily:
UIImageView *imageView = emotionViewDictionary[#"Frightened"];
By the way, boolean values in Objective-C are called YES and NO and not true and false.
I'm working with an image heavy iOS app and I found myself typing almost the same line again and again:
...
A016.image = [UIImage imageNamed:img21];
A017.image = [UIImage imageNamed:img21];
A018.image = [UIImage imageNamed:img21];
...
Now I ask you: is there a way where I could store the UIImageViews names in an Array or something?
Only to beautify my very ugly code.
/John
Yes, you can put the UIImageViews in an array and put it in a for.
UIImageView * imageView1;
UIImageView * imageView2;
UIImageView * imageView3;
NSArray * imageViewsArray = [NSArray arrayWithObjects:imageView1,imageView2,imageView3,nil];
for (UIImageView * currentImageView in imageViewsArray) {
currentImageView.image = [UIImage imageNamed:img21];
}
Of course you can simplify something like that. But it's not entirely clear what the context is exactly.
If you have all your image views in an array you could do something like this.
// Assume an NSArray called imageViews exists with all the UIImageView instances in it.
for (UIImageView *imageView in imageViews) {
imageView.image = [UIImage imageNamed:img21];
}
If your image views aren't in an array already and are actually called A016, A017 etc., then I'd recommend you change your code design. Something like this is never a good idea. It results in bad, difficult to maintain code. If this is some kind of table of images, try putting the image views in an array in the first place.
That being said, there are ways to put variables like that in an array. If they are declared as #properties or ivars you can could do something like this.
NSMutableArray *imageViews = [NSMutableArray arrayWithCapacity:20];
for (int i = 0; i < 20; i++) {
NSString *variableName = [NSString stringWithFormat:#"A0%d", i];
UIImageView *imageView = [self valueForKey:variableName];
[imageViews addObject:imageView];
}
After that you can save the array as an ivar and do the same thing as above.
A more hardcoded version would be to simply put the image views into an array yourself:
NSArray *imageViews = [NSArray arrayWithObjects:..., A016, A017, A018,..., nil];
But I really recommend not using indexed variable names like that.
I'm writing a sort of calculator app. I have a UIPickerView (1 column) loading data from an NSArray of strings. The user will select one of these (it's selecting which type of calculator to use -- each uses a different method to calculate). The user inputs some things into some UITextFields and then presses a UIButton to do the calculations.
My NSArray is this:
calcNames = [NSArray alloc] initWithObjects:#"first", #"second", #"third", nil];
And my methods are called firstCalc(input1, input2, input3), secondCalc(input1, input2, input3), and so on. (The inputs are coming from the UITextFields.)
When I press the button, I would like to tell it to look at what the selection in the UIPickerView is and run the corresponding method without just typing an if-then statement for each one (it's very inconvenient to do this for reasons specific to my app, which are beyond the scope of this discussion).
So I have already defined a way to determine what the selected calc is:
selectedCalc = [[NSString alloc] initWithString:[calcNames objectAtIndex:row]]
where 'row' is the current selection in the UIPickerView.
Now I have a doCalculations method for when someone presses the UIButton:
-(IBAction)doCalculations:(id)sender {
// save the data input
double input1 = [input1Field.text doubleValue];
double input2 = [input2Field.text doubleValue];
double input3 = [input3Field.text doubleValue];
// do the calculations
int i;
for (i = 0; i < [calcNames count]; i++) {
if (selectedCalc == [calcNames objectAtIndex:i]) {
// do calculations here
double numResult = ??????
// if selectedCalc is "first", I want it to do firstCalc(input 1, input 2, input 3)
// if selectedCalc is "second", I want it to do secondCalc(input 1, input 2, input 3), and so on
// the rest is just for displaying the result
NSString* result = [NSString stringWithFormat:#"The answer is %f", numResult];
[resultLabel setText:result];
}
}
}
So basically, it runs a for loop until it finds which calculator is selected from the UIPickerView and when it finds it, runs the calculations and displays them.
I've been trying to understand if maybe function pointers or selectors (NSSelectorFromString?) are the right things to use here and how to use them, but I'm really struggling to understand where to go after a couple days of reading Apple's documentation, Stack Overflow questions, playing with sample code, and tinkering with my own code.
Sorry if the question is too lengthy, I thought it may be more helpful to others looking for assistance in the future to see the full idea. (At least I know sometimes I'm lost with these question pages.)
I would be very grateful for any assistance,
Ryan
You can dynamically invoke a method using a selector. You could for example have a secondary array to calcNames with selector called calcSelectors:
SEL calcSelectors[] = (SEL[3]){
#selector(first:arg:),
#selector(second:arg:),
#selector(third:arg:)};
Calling the right method would then be as simple as:
[self performSelector:calcSelectors[calcIndex] withObject:arg1 withObject:arg2];
If you need more then 2 arguments, then you also need to mess a bit with a NSInvocation instance to setup the call.
Example 1:
NSString *method=[calcNames objectAtIndex:0];//here play with objectatindex
SEL s=NSSelectorFromString(method);
[self performSelector:s];
which will call this method
-(void)first{
NSLog(#"first");
}
-----------------------------------------
Example 2:
NSString *totalMethodName;
totalMethodName=#"vijay";
totalMethodName=[totalMethodName stringByAppendingString:#"With"];
totalMethodName=[totalMethodName stringByAppendingString:#"Apple"];
SEL s=NSSelectorFromString(totalMethodName);
[self performSelector:s];
will call
-(void)vijayWithApple{
NSLog(#"vijayWithApple called");
}
You can make use of NSInvocation to dynamically bind multiple arguments to a selector. Follow this post to learn it.
If you are going to use NSInvocation you have to define your methods in the objective-C way something like the following.
- (double)firstCalcWithInput1:(double)input1 input2:(double)input2 andInput3:(double)input3;
- (double)secondCalcWithInput1:(double)input1 input2:(double)input2 andInput3:(double)input3;