I have an app that have a lot of records that i am loading into a core data DB. The actual loading is done in a module called "loadDBRecords". This module is called from "MainViewController", which is connected to "MainViewController.xib".
As the loading takes quite some time i have added an UIActivityIndicatorView to the .xib during the load. However, i would like to use a UIProgressView. When i look at this i do not see any way of using that unless i move the loading code from "loadDBRecords" to the "MainViewController".
My question is: What is the best way of leveraging the UIProgressView with my setup?
You could add a "progressHandler" block to the -loadDBRecords method. Execute the block for every record you load, and pass back a floating-point value between 0.0 and 1.0 indicating the progress thus far. The block can then assign that value to the progress bar, or print it to the console, or whatever you need it to do. (Traditionally, this would be done with a function pointer or a delegate/selector combination, but I've found blocks tend to make your intent clearer—or at least make it easier to show your intent.)
- (void)loadDBRecords:(void (^)(CGFloat progress))progressHandler {
NSUInteger count = /* number of records*/;
for (NSUInteger i = 0; i < count; i++) {
/* load the record */
progressHandler((CGFloat)n / (CGFloat)count);
}
}
Related
I am trying to implement a system so that it retrieves sound and extracts the mfcc of it. I'd like to implement my own mfcc function because librosa library wasn't implemented in C and other implementations of mfcc extractions doesn't yield the same outputs as librosa library does.
So I wrote a code, however, when I would like create hanning window, program doesn't take a step further and always stays the same statement while debugging. The statement is below:
float *mul = malloc(sizeof(float)*fftsize);
The whole code is as follows:
float* hanning(int fftsize){
float *mul = malloc(sizeof(float)*fftsize);
for (int i = 0; i<fftsize; i++){
mul[i] = 0.5 * (1 - cos(2*PI*i/(fftsize-1)));
}
return mul;
}
I put an LCD code to all error handler functions in stm32f7xx_it.c file to determine which fault I'm facing, and I see that it is hard_fault.
So what's the problem? I hope the issue is explained clearly. Due to the privacy, I couldn't put here whole code. Sorry for that. Thx in advance for your response.
Edit: I am chaning malloc to normal array with a variable length array. But still it takes me to HardFault_Handler function. SCB->SHCSR returns sometimes 65535 and sometimes 1.
I am trying to write an app that has a multiple choice quiz in it. I am writing it in a simple and somewhat hardcoded way. I have created an array of questions and a 2-d array of answers as my "database". My problem is that when i am iterating over the loop, my app immediately goes to the last question, even though if statements that in an ideal world should let the user interact with every questions.
my while loop is
var i = 0;
while i<10 then
make the question view
make the answer view
make the answers clickable
calculate scoring
if the next button is pushed and i < 8 then i+=1
/*this prevents the app from building but when i put the i+=1 outside this control statement it goes directly to the last question in my database*/
end While
any ideas? my code is really long and do not know if i should post it
Rather than doing it all in a while loop, you should take a slightly different approach.
Create a function that does the while-loop-block above, and use a variable to keep track of the currently displayed question and answer. Then when the user clicks next, advance to the next pair, until the user is done.
var current = 0, until = 10;
function showCurrent() {
// make the question view
// make the answer view
// make the answers clickable
// calculate scoring
}
function goToNext() {
current += 1;
if (current === until) {
// carry on with whatever is next
}
else {
showCurrent();
}
}
showCurrent();
I am writing a iPhone app that calls a web service. Let say the web service returns 1000 elements in the json object. I don't want to load all 1000 of them since parsing can take some time. What I would like to do is load the first 15 elements of the NSDictionary that I created from the json object and then when the user scrolls to the bottom of the tableview have a 16th row that says "load more....". Since I already have all of the data stored in the NSDictionary object is there a way to break this up so that it returns the 15, then the user clicks "load more...." and it loads the next 15 and continues until there are no more elements in the NSDictionary? I can present examples of my code but I am wondering if anyone has an example of how to accomplish this. Thanks in advance for any assistance.
i think a UITableView does this for you. Only the visible cells are ever constructed. Their memory is then swapped with the next rows as you scroll down. I don't see a point in re-inventing the wheel.
Also as a note, only the visible cells are "parsed" as you put it. It will not construct a cell for every item in your datasource on load.
Assuming I hear you correctly I would say you just need a little tricky logic to get this working
I would simply maintain an index offset which I would multiply by the amount of rows you want to show at any time(15 in your case)
Your logic is to always return the amount of rows that you want to allow + 1 for the final. ex: return _indexOffset * 15 + 1; //for your numberOfRowsForSection
In your didSelectIndexPathOf you check if you're the last row:
if(indexPath.row == _indexOffset * 15)
{
_indexOffset ++;
[tableView reloadData];
}
This isn't an exact answer but I think it can get you started
I'm creating a simple app which has a list of characters and a list of (4) players, the players is simply a reference to a playable character.
I'm stuck on how to do the following:
Make a reference to the current player on turn
Find out who the next player on turn is
Handling the last player so that it will return to the first player on turn.
Ideally, I would like to be able to do AFTER, FIRST, LAST BEFORE commands on a NSMutableArray, of these I'm able to do lastObject, but there is no firstObject, afterObject, etc.
I believe you can fake BEFORE,AFTER,FIRST commands with objectAtIndex; but ideally I do not want to rely on numeric references because it could be incorrect -- also if its mutable, the size will always change.
Typically, I would be able to do the following in Pseudocode.
Global player_on_turn.player = Null //player_on_turn is a pointer to the player object
; Handle next player on turn
If (player_on_turn.player = Null) Then Error("No player on turn assigned")
If (sizeOf[playerList]==0) Then Error("There are no players in the game")
If After player_on_turn = null Then
; We reset it
player_on_turn.player = First player
Else
; Move to the next player on turn
player_on_turn.player = After player_on_turn.player
End If
With this in mind, what is the best strategy to help handle a player on turn concept as described in the 1-2-3 example above.
Thanks
It probably doesn’t matter what data structure you’re using - at some level you will have to rely on a numerical index (except if you are using linked lists). And this is alright. If you don’t want to use it in your main game implementation that is alright, too. Just create a class that encapsulates those things. First think of the operations you need it to support. My guess here would be those:
- (PlayerObject *) currentPlayer;
- (void) startNextTurn;
If you have this you can write your game using those primitives and worry about how to best implement that later. You can change those at any time without breaking your actual game.
My recommendation would be something like this:
- (PlayerObject *) currentPlayer; {
return [players objectAtIndex: currentPlayerIndex];
}
- (void) startNextTurn; {
++currentPlayerIndex;
if (currentPlayerIndex >= [players count]) {
currentPlayerIndex = 0;
}
}
Using the index there is OK, even if the array is mutable. If you have methods that change the player array they also can take care of the necessary changes to the currentPlayerIndex.
Having this object makes it easy to write unit tests. The global variable you suggest in your pseudo-code makes it impossible to write meaningful unit tests.
Use a State Pattern for the main runloop of the software. Draw it out as a diagram and create variables to control which state the system is in.
You should use a circular list of the players to return current, next, and previous players.
This is also a great question for GameDev on the Stack Exchange.
PS
CocoaHeads puts out a relatively nice set of data objects, including a circular buffer.
first post here so sorry for the length of it. I've been lurking and learning a lot so far but now I have to step in and ask a question. I have read numerous posts here as advised in the FAQs, but I couldn’t find exactly the answer I’m looking for.
Before anything else, let me just say that I'm a total beginner in programming (let alone Objective-C) so please excuse me for any misuse of the terminology. Same goes for any funny english as english not my native language.
I'm building an unit conversion application with a main window containing (among other stuff) two popUpButtons. I'm using indexOfSelectedItem from both popUpButtons in order to calculate a float value (I'm getting the indexes initially in the AwakeFromNib and later in the pop up buttons controller method, when the user change selection).
My problem consists of two parts: first, the code for calculation of that float is pretty massive as I'm comparing every combination of the two indexes of selected items. And second, I would need to have the calculated float value available immediately after launch as the user might want to perform a conversion before using any of the window popUpButtons (otherwise I would put the calculation code in a -(IBAction) method).
So, I'm trying with the following code for calculation of the float value:
#interface MyClass: NSObject
float calculatedFloat;
-(void)setCalculatedFloat:(float)calcFl;
-(float)calculatedFloat;
#implementation MyClass
-(void)setCalculatedFloat:(float)calcFl {
calcFl = 1.0; // I'm simplifying, this is where I'd like to perform calculation
}
-(float)calculatedFloat {
return calculatedFloat;
}
Now, for the first part of my problem, when I use the calculatedFloat in another method, say:
-(void)printIt {
NSLog(#"Calculated float equals: %.2f", calulatedFloat);
}
all I receive in Debugger is 0.00.
First question would be: if this is not working, how do I properly access this value from within another method?
For the second part of the problem, I'm using -(void)AwakeFromNib; to set up popUpButtons etc. right after the launch but I really wouldn't like to put all of the float calculation code in it only to repeat it somewhere else later.
So the second question would be: is this even possible what I'm trying to achieve? Further more, do I need to move this calculation code to another class? If so, how can I make that other class aware of the indexOfSelectedItem from a popUpButton?
Sorry for the lengthy post and possibly confusing and silly questions. I hope you didn't have to cringe your teeth too much while reading! :)
Thanks!
-(void)setCalculatedFloat:(float)calcFl {
calcFl = 1.0; // I'm simplifying, this is where I'd like to perform calculation
}
This doesn't show up when you print it later because you assigned to the variable holding the new value, not the variable for the value of the property. You need to assign to your calulatedFloat instance variable.
(You typo'ed that variable name, BTW.)
You should move the calculating into another method, and send yourself that message from awakeFromNib and from anywhere that needs to cause recalculation. That method should call setCalculatedFloat: with the calculated value—i.e., setCalculatedFloat: should be just a simple setter. Once you make that change, you could replace your custom accessors with a #synthesize statement and let the compiler write the accessors for you.
My problem consists of two parts: first, the code for calculation of that float is pretty massive as I'm comparing every combination of the two indexes of selected items.
You might see whether you can create custom objects to set as the menu items' representedObject properties, in order to cut out this massive comparison tree. It's hard to be more specific about this without knowing what your comparison tree does.