Classes/PeriodicElements.m

/*
     File: PeriodicElements.m
 Abstract: Encapsulates the collection of elements and returns them in presorted states.
  Version: 1.12
 
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#import "PeriodicElements.h"
#import "AtomicElement.h"
 
@implementation PeriodicElements
 
// we use the singleton approach, one collection for the entire application
static PeriodicElements *sharedPeriodicElementsInstance = nil;
 
+ (PeriodicElements *)sharedPeriodicElements {
    @synchronized(self) {
        static dispatch_once_t pred;
        dispatch_once(&pred, ^{ sharedPeriodicElementsInstance = [[self alloc] init]; });
    }
    return sharedPeriodicElementsInstance;
}
 
+ (id)allocWithZone:(NSZone *)zone {
    @synchronized(self) {
        if (sharedPeriodicElementsInstance == nil) {
            sharedPeriodicElementsInstance = [super allocWithZone:zone];
            return sharedPeriodicElementsInstance;  // assignment and return on first allocation
        }
    }
    return nil; //on subsequent allocation attempts return nil
}
 
- (id)copyWithZone:(NSZone *)zone {
    return self;
}
 
// setup the data collection
- init {
    if (self = [super init]) {
        [self setupElementsArray];
    }
    return self;
}
 
- (void)setupElementsArray {
    
    NSDictionary *eachElement;
    
    // create dictionaries that contain the arrays of element data indexed by
    // name
    self.elementsDictionary = [NSMutableDictionary dictionary];
    // physical state
    self.statesDictionary = [NSMutableDictionary dictionary];
    // unique first characters (for the Name index table)
    self.nameIndexesDictionary = [NSMutableDictionary dictionary];
 
    // create empty array entries in the states Dictionary or each physical state
    [self.statesDictionary setObject:[NSMutableArray array] forKey:@"Solid"];
    [self.statesDictionary setObject:[NSMutableArray array] forKey:@"Liquid"];
    [self.statesDictionary setObject:[NSMutableArray array] forKey:@"Gas"];
    [self.statesDictionary setObject:[NSMutableArray array] forKey:@"Artificial"];
    
    // read the element data from the plist
    NSString *thePath = [[NSBundle mainBundle]  pathForResource:@"Elements" ofType:@"plist"];
    NSArray *rawElementsArray = [[NSArray alloc] initWithContentsOfFile:thePath];
 
    // iterate over the values in the raw elements dictionary
    for (eachElement in rawElementsArray)
    {
        // create an atomic element instance for each
        AtomicElement *anElement = [[AtomicElement alloc] initWithDictionary:eachElement];
        
        // store that item in the elements dictionary with the name as the key
        [self.elementsDictionary setObject:anElement forKey:anElement.name];
        
        // add that element to the appropriate array in the physical state dictionary 
        [[self.statesDictionary objectForKey:anElement.state] addObject:anElement];
        
        // get the element's initial letter
        NSString *firstLetter = [anElement.name substringToIndex:1];
        NSMutableArray *existingArray = [self.nameIndexesDictionary valueForKey:firstLetter];
        
        // if an array already exists in the name index dictionary
        // simply add the element to it, otherwise create an array
        // and add it to the name index dictionary with the letter as the key
        //
        if (existingArray != nil)
        {
            [existingArray addObject:anElement];
        } else {
            NSMutableArray *tempArray = [NSMutableArray array];
            [self.nameIndexesDictionary setObject:tempArray forKey:firstLetter];
            [tempArray addObject:anElement];
        }
    }
    
    // create the dictionary containing the possible element states
    // and presort the states data
    self.elementPhysicalStatesArray = [NSArray arrayWithObjects:@"Solid", @"Liquid", @"Gas", @"Artificial", nil];
    [self presortElementsByPhysicalState];
    
    // presort the dictionaries now
    // this could be done the first time they are requested instead
    //
    [self presortElementInitialLetterIndexes];
    
    self.elementsSortedByNumber = [self presortElementsByNumber];
    self.elementsSortedBySymbol = [self presortElementsBySymbol];
}
 
// return the array of elements for the requested physical state
- (NSArray *)elementsWithPhysicalState:(NSString *)aState {
    
    return [self.statesDictionary objectForKey:aState];
}
 
// presort each of the arrays for the physical states
- (void)presortElementsByPhysicalState {
    
    for (NSString *stateKey in self.elementPhysicalStatesArray) {
        [self presortElementsWithPhysicalState:stateKey];
    }
}
 
- (void)presortElementsWithPhysicalState:(NSString *)state {
    
    NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name"
                                                                   ascending:YES
                                                                    selector:@selector(localizedCaseInsensitiveCompare:)] ;
    
    NSArray *descriptors = [NSArray arrayWithObject:nameDescriptor];
    [[self.statesDictionary objectForKey:state] sortUsingDescriptors:descriptors];
}
 
// return an array of elements for an initial letter (ie A, B, C, ...)
- (NSArray *)elementsWithInitialLetter:(NSString*)aKey {
    
    return [self.nameIndexesDictionary objectForKey:aKey];
}
 
// presort the name index arrays so the elements are in the correct order
- (void)presortElementInitialLetterIndexes {
    
    self.elementNameIndexArray = [[self.nameIndexesDictionary allKeys] sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
    for (NSString *eachNameIndex in self.elementNameIndexArray) {
        [self presortElementNamesForInitialLetter:eachNameIndex];
    }
}
 
- (void)presortElementNamesForInitialLetter:(NSString *)aKey {
    
    NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name"
                                                                   ascending:YES
                                                                    selector:@selector(localizedCaseInsensitiveCompare:)] ;
    
    NSArray *descriptors = [NSArray arrayWithObject:nameDescriptor];
    [[self.nameIndexesDictionary objectForKey:aKey] sortUsingDescriptors:descriptors];
}
 
// presort the elementsSortedByNumber array
- (NSArray *)presortElementsByNumber {
    
    NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"atomicNumber"
                                                                   ascending:YES
                                                                    selector:@selector(compare:)] ;
    
    NSArray *descriptors = [NSArray arrayWithObject:nameDescriptor];
    NSArray *sortedElements = [[self.elementsDictionary allValues] sortedArrayUsingDescriptors:descriptors];
    return sortedElements;
}
 
// presort the elementsSortedBySymbol array
- (NSArray *)presortElementsBySymbol {
    
    NSSortDescriptor *symbolDescriptor = [[NSSortDescriptor alloc] initWithKey:@"symbol"
                                                                   ascending:YES
                                                                    selector:@selector(localizedCaseInsensitiveCompare:)] ;
    
    NSArray *descriptors = [NSArray arrayWithObject:symbolDescriptor];
    NSArray *sortedElements = [[self.elementsDictionary allValues] sortedArrayUsingDescriptors:descriptors];
    return sortedElements;
}
 
@end