(because I googled it, and on the first page of hits I couldn’t find any copy\/pasteable source for this common problem, here’s an answer with (poor) public domain source code)
\n
\nIn Objective-C \/ Cocoa, you cannot sort a dictionary (which is what I’m about to fix…). You cannot place any kind of persistent ordering onto a dictionary.<\/p>\n
(this is a common requirement in modern software, such that you expect any standard lib to contain a core class to handle it. For instance, Java’s LinkedHashMap…)<\/p>\n
I would prefer a standard-lib solution, especially since it’ll have all the features, and probably no bugs – and it’s more likely to be optimized for performance. But, since Apple hasn’t given us one, here’s the lazy-and-quick way to do it:<\/p>\n
It’s that easy … and yet, because Apple didn’t do it, you have to re-write this class every time you start a new project. Sigh.<\/p>\n
There’s one issue with this – for the allKeys method, I did a “copy”, which I probably shouldn’t have (I wasn’t really thinking carefully about i), which means you’ll have to remember to release the reference you receive – or else change that to:<\/p>\n
\nreturn underlyingArray;\n<\/p><\/blockquote>\n
or:<\/p>\n
\nreturn [[underlyingArray copy] autorelease];\n<\/p><\/blockquote>\n
or, perhaps best of all:<\/p>\n
\nreturn [NSArray arrayWithContentsOfArray: underlyingArray]; \/\/ returns an Immutable result; nice and safe!\n<\/p><\/blockquote>\n
Here’s my quick hack code, in its entirety:<\/p>\n
\n
\n#import \"SortedDictionary.h\"<\/p>\n@implementation SortedDictionary
\n@synthesize underlyingArray, underlyingDictionary;<\/p>\n-(id) init
\n{
\n\tif( self = [super init] )
\n\t{
\n\t\tunderlyingArray = [[NSMutableArray alloc] init];
\n\t\tunderlyingDictionary = [[NSMutableDictionary alloc] init];
\n\t}
\n\treturn self;
\n}<\/p>\n-(id)objectForKey:(id)aKey
\n{
\n\treturn [underlyingDictionary objectForKey:aKey];
\n}<\/p>\n-(id)valueForKey:(NSString *)key
\n{
\n\treturn [underlyingDictionary valueForKey:key];
\n}<\/p>\n-(NSUInteger)count
\n{
\n\treturn [underlyingDictionary count];
\n}<\/p>\n\/** Ordered... *\/
\n-(NSArray *)allKeys
\n{
\n\treturn [underlyingArray copy];
\n}<\/p>\n-(NSArray *)allValues
\n{
\n\treturn [underlyingDictionary allValues];
\n}<\/p>\n\/** Preserves current order, or does ordered ADD if the key isn't already present *\/
\n-(void)setObject:(id)anObject forKey:(id)aKey
\n{
\n\tif( [underlyingDictionary objectForKey:aKey] == nil )
\n\t{
\n\t\t[self addObject:anObject forKey:aKey];
\n\t}
\n\telse
\n\t{
\n\t\t[underlyingDictionary setObject:anObject forKey:aKey];
\n\t}
\n}<\/p>\n\/** Preserves current order, or does ordered ADD if the key isn't already present *\/
\n-(void)setValue:(id)value forKey:(NSString *)key;
\n{
\n\tif( [underlyingDictionary objectForKey:key] == nil )
\n\t{
\n\t\t[self addValue:value forKey:key];
\n\t}
\n\telse
\n\t{
\n\t\t[underlyingDictionary setValue:value forKey:key];
\n\t}
\n}<\/p>\n-(void)removeObjectForKey:(id)aKey
\n{
\n\t[underlyingArray removeObject:aKey];
\n\t[underlyingDictionary removeObjectForKey:aKey];
\n}<\/p>\n-(void)removeAllObjects
\n{
\n\t[underlyingArray removeAllObjects];
\n\t[underlyingDictionary removeAllObjects];
\n}<\/p>\n-(void)addObject:(id)anObject forKey:(id)aKey
\n{
\n\tif( [underlyingDictionary objectForKey:aKey] == nil )
\n\t{
\n\t\t[underlyingArray addObject:aKey];
\n\t\t[underlyingDictionary setObject:anObject forKey:aKey];
\n\t}
\n\telse
\n\t{
\n\t\tNSLog( @\"[%@] ERROR: attempted to addObject a key that already exists in this dictionary: %@\", [self class], aKey );
\n\t}
\n}<\/p>\n-(void)addValue:(id)value forKey:(NSString *)key
\n{
\n\tif( [underlyingDictionary objectForKey:key] == nil )
\n\t{
\n\t\t[underlyingArray addObject:key];
\n\t\t[underlyingDictionary setValue:value forKey:key];
\n\t}
\n\telse
\n\t{
\n\t\tNSLog( @\"[%@] ERROR: attempted to addValue a key that already exists in this dictionary: %@\", [self class], key );
\n\t}
\n}<\/p>\n@end
\n<\/code>\n<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"(because I googled it, and on the first page of hits I couldn’t find any copy\/pasteable source for this common problem, here’s an answer with (poor) public domain source code)<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[51,20],"tags":[],"_links":{"self":[{"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/posts\/697"}],"collection":[{"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/comments?post=697"}],"version-history":[{"count":0,"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/posts\/697\/revisions"}],"wp:attachment":[{"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/media?parent=697"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/categories?post=697"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/new.t-machine.org\/index.php\/wp-json\/wp\/v2\/tags?post=697"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}