Here's a bit of a newbie question.
I have a NSMutableDictionary *dict
which in the log looks like this:
"test1" = "5";
"test2" = "78";
"test3" = "343";
"test4" = "3";
I need to print each number by itself, but I'm pretty poor at arrays and FOR-sentences.
I was thinking something like:
for (dict) {
double number = [[[dict allKeys] objectAtIndex:0] doubleValue];
NSLog(#"Number: %f",number);
}
Which I want to look like this in the log on each line:
Number: 5
Number: 78
Number: 343
Number: 3
But obviously my "FOR"-method is gibberish.
Any help would be appreciated.
You use a fast enumeration for to do this. It iterates over all the keys in the dictionary:
for (NSString *key in dict) {
double number = [[dict objectForKey:key] doubleValue];
NSLog(#"Number: %f", number);
}
Using blocks:
NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
#"5", #"test1",
#"78", #"test2",
#"343", #"test3",
#"3", #"test4",
nil];
[dictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
NSLog(#"Number: %#", obj);
}];
NSLog output:
Number: 5
Number: 3
Number: 343
Number: 78
If you just want to log these numbers, try the following:
for (NSString *number in dict) {
NSLog(#"Number: %#",[dict objectForKey:number]);
}
The first answer has two objects being created with the name "number". Instead do:
for (NSString *key in dict) {
NSLog(#"Number as double: %f", [[dict objectForKey:key] doubleValue]);
NSLog(#"Number as string: %#", [dict objectForKey:key]);
}
What's great about fast enumeration is that it creates the object for you (and auto-release them). The key is what's being given to you when fast-enumerating through NSDictionaries. Because you now have the key, you just grab the objectAtKey. In your case, it's a string in your dictionary, so you'll have to either convert it to a double (or whatever type you need), or output as a string. I added examples for both cases above. Good luck!
As already mentioned fast-enumeration is preferable in these cases, but you could also do something like this:
for (int i =0; i<[dict count]; i++){
NSString *str=[dict objectForKey:[NSString stringWithFormat:#"test%d",i+1]];
NSLog(#"%#",str);
}
Related
I have a NSMutableDictionary and I want to swap values & keys. i.e, after swapping values becomes keys and its corresponding keys with become values All keys and values are unique. Looking for an in place solution because size is very big . Also, the keys and values are NSString objects
NSMutableDictionary *d = [NSMutableDictionary dictionaryWithDictionary:#{
#"key1" : #"value1",
#"key2" : #"value2"}];
for (NSString *key in [d allKeys]) {
d[d[key]] = key;
[d removeObjectForKey:key];
}
NSLog(#"%#", d); // => { value1 : key1,
// value2 : key2 }
Assumptions
unique values (as they will become keys)
values conform to NSCopying (same as above)
no value is equal to any key (otherwise colliding names will be lost in the process)
Here is another way to invert dictionary. The simplest for me.
NSArray *keys = dictionary.allKeys;
NSArray *values = [dictionary objectsForKeys:keys notFoundMarker:[NSNull null]];
[dictionary removeAllObjects]; // In case of huge data sets release the contents.
NSDictionary *invertedDictionary = [NSDictionary dictionaryWithObjects:keys forKeys:values];
[dictionary setDictionary:invertedDictionary]; // In case you want to use the original dictionary.
EDIT: I had written a few lines of codes to get the OP started into the task of creating his own algorithm. The answer was not well received so I have crafted a full implementation of an algorithm that does what he asks, and goes one step further.
Advantages:
Makes no assumptions regarding the contents of the dictionary, for example, the values need not conform to the 'NSCopying' protocol
Transverses the whole hierarchy of a collection, swapping all the keys
It's fast since it uses recursion and fast enumeration
Does not alter the contents of the original dictionary, it creates a brand new one
Code has been implemented through categories to both collections:
#interface NSDictionary (Swapping)
- (NSDictionary *)dictionaryBySwappingKeyWithValue;
#end
#interface NSDictionary (Swapping)
- (NSDictionary *)dictionaryBySwappingKeyWithValue
{
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithCapacity:self.count];
[self enumerateKeysAndObjectsUsingBlock:^(id key, id value, BOOL *stop) {
id newKey = nil;
if ([value isKindOfClass:[NSDictionary class]]) {
newKey = [value dictionaryBySwappingKeyWithValue];
} else if ([value isKindOfClass:[NSArray class]]) {
newKey = [value arrayBySwappingKeyWithValue];
} else {
newKey = value;
}
if (![newKey conformsToProtocol:#protocol(NSCopying)]) {
newKey = [NSValue valueWithNonretainedObject:newKey];
}
mutableDictionary[newKey] = key;
}];
return [NSDictionary dictionaryWithDictionary:mutableDictionary];
}
#end
and...
#interface NSArray (Swapping)
- (NSArray *)arrayBySwappingKeyWithValue;
#end
#implementation NSArray (Swapping)
- (NSArray *)arrayBySwappingKeyWithValue
{
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:self.count];
[self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj isKindOfClass:[NSDictionary class]]) {
NSDictionary *newDict = [obj dictionaryBySwappingKeyWithValue];
mutableArray[idx] = newDict;
} else if ([obj isKindOfClass:[NSArray class]]) {
NSArray *newArray = [obj arrayBySwappingKeyWithValue];
mutableArray[idx] = newArray;
} else {
mutableArray[idx] = obj;
}
}];
return [NSArray arrayWithArray:mutableArray];
}
#end
As an example, assume you have a dictionary with the following structure:
UIView *view = [[UIView alloc] init];
NSDictionary *dict = #{#"1" : #"a",
#"2" : #[ #{ #"5" : #"b" } ],
#"3" : #{#"6" : #"c"},
#"7" : view};
NSDictionary *newDict = [dict dictionaryBySwappingKeyWithValue];
Printing the newDict object in the console will give you this output:
(lldb) po mutableDictionary
{
a = 1;
({b = 5;}) = 2;
{c = 6;} = 3;
"<30b50617>" = 7;
}
As you can see, not only have the keys and values been swapped at the first level of the hierarchy, but deep inside each collection.
"<30b50617>" represents the UIView object wrapped inside a NSValue. Since UIView does not comply to the NSCopying protocol, it needs to be handled this way if you want it to be a key in your collection.
Note: Code was done in a couple of minutes. Let me know if I missed something.
for (NSString *key in [myDictionary allKeys]) {
NSString *value = [responseDataDic objectForKey:key];
[myDictionary removeObjectForKey:key];
[myDictionary addObject:key forKey:value];
}
Assumption:
No key = value;
Complexity:
No extra space required. Will loop through once and replace all key value pairs.
NSArray* allKeys = [theDict allKeys];
NSArray* allValues = [theDict allValues];
NSMutableDictionary* newDict = [NSMutableDictionary dictionaryWithObjects:allKeys forKeys:allValues];
I have an NSMutableArray that looks like this
{
"#active" = false;
"#name" = NAME1;
},
{
"#active" = false;
"#name" = NAME2;
}
Is there a way to convert this to an NSDictionary and then use objectForKey to get an array of the name objects? How else can I get these objects?
There is a even shorter form then this proposed by Hubert
NSArray *allNames = [array valueForKey:#"name"];
valueForKey: on NSArray returns a new array by sending valueForKey:givenKey to all it elements.
From the docs:
valueForKey:
Returns an array containing the results of invoking
valueForKey: using key on each of the array's objects.
- (id)valueForKey:(NSString *)key
Parameters
key The key to retrieve.
Return Value
The value of the retrieved key.
Discussion
The returned array contains NSNull elements for each object that returns nil.
Example:
NSArray *array = #[#{ #"active": #NO,#"name": #"Alice"},
#{ #"active": #NO,#"name": #"Bob"}];
NSLog(#"%#\n%#", array, [array valueForKey:#"name"]);
result:
(
{
active = 0;
name = Alice;
},
{
active = 0;
name = Bob;
}
)
(
Alice,
Bob
)
If you want to convert NSMutableArray to corresponding NSDictionary, just simply use mutableCopy
NSMutableArray *phone_list; //your Array
NSDictionary *dictionary = [[NSDictionary alloc] init];
dictionary = [phone_list mutableCopy];
This is an Array of Dictionary objects, so to get the values you would:
[[myArray objectAtIndex:0]valueForKey:#"name"]; //Replace index with the index you want and/or the key.
This is example one of the exmple get the emplyee list NSMutableArray and create NSMutableDictionary.......
NSMutableArray *emloyees = [[NSMutableArray alloc]initWithObjects:#"saman",#"Ruchira",#"Rukshan",#"ishan",#"Harsha",#"Ghihan",#"Lakmali",#"Dasuni", nil];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
for (NSString *word in emloyees) {
NSString *firstLetter = [[word substringToIndex:1] uppercaseString];
letterList = [dict objectForKey:firstLetter];
if (!letterList) {
letterList = [NSMutableArray array];
[dict setObject:letterList forKey:firstLetter];
}
[letterList addObject:word];
} NSLog(#"dic %#",dict);
yes you can
see this example:
NSDictionary *responseDictionary = [[request responseString] JSONValue];
NSMutableArray *dict = [responseDictionary objectForKey:#"data"];
NSDictionary *entry = [dict objectAtIndex:0];
NSString *num = [entry objectForKey:#"num"];
NSString *name = [entry objectForKey:#"name"];
NSString *score = [entry objectForKey:#"score"];
im sorry if i can't elaborate much because i am also working on something
but i hope that can help you. :)
No, guys.... the problem is that you are stepping on the KeyValue Mechanism in cocoa.
KeyValueCoding specifies that the #count symbol can be used in a keyPath....
myArray.#count
SOOOOOO.... just switch to the ObjectForKey and your ok!
NSMutableDictionary *myDictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:#"theValue", #"#name", nil];
id kvoReturnedObject = [myDictionary valueForKey:#"#name"]; //WON'T WORK, the # symbol is special in the valueForKey
id dictionaryReturnedObject = [myDictionary objectForKey:#"#name"];
NSLog(#"object = %#", dictionaryReturnedObject);
I am having an array like fallowing,
NSArray*array = [NSArray arrayWithObjects:#"1.1 something", #"1.2 something else", #"1.3 out of left field", #"1.4 yet another!", nil];
Now,i am having the string like fallowing,
NSString*str = #"1.3";
Now i will send the str .Then it needs to find that str in array and it need to return the index of object where that text found.Means i need index 2 has to come as output.Can anyone share the code please.Thanks in advance.
Here is an example using blocks, notice the method: hasPrefix:
NSArray *array = [NSArray arrayWithObjects:#"1.1 problem1", #"1.2 problem2", #"1.3 problem3", #"1.4 problem4", nil];
NSString *str = #"1.3";
NSUInteger index = [array indexOfObjectPassingTest:
^(id obj, NSUInteger idx, BOOL *stop) {
return [obj hasPrefix:str];
}];
NSLog(#"index: %lu", index);
NSLog output:
index: 2
First a comment,
NSString *str = 1.3;
does not create an NSString object. You should instead have
NSString *str = #"1.3";
To search the NSArray, you will either have to change the string to the exact string in the array or search the NSString as well. For the former, simply do
float num = 1.3;
NSString *str = [NSString stringWithFormat:#"%.1f problem%d",num,(num*10)%10];
[array indexOfObject:str];
You can get fancier using NSPredicates as well.
Try
NSString *searchString = [str stringByAppendingFormat: #" problem%#", [str substringFromIndex: 2]];
NSUInteger index = [array indexOfObject: searchString];
Or (because you somehow like oneliners):
[array indexOfObject: [[array filteredArrayUsingPredicate: [NSPredicate predicateWithFormat: #"SELF beginswith %#", str]] objectAtIndex: 0]];
The simplest way is to enumerate through values of array and check substrings:
NSArray *array = [NSArray arrayWithObjects: #"1.1 something", #"1.2 something else", #"1.3 out of left field", #"1.4 yet another!", nil];
NSString *str = #"1.33";
int i = -1;
int index = -1;
for (NSString *arrayString in array) {
i++;
if ([arrayString rangeOfString: str].location != NSNotFound) {
index = i;
break;
}
}
NSLog(#"Index: %d", index);
Not optimal but will work.
I am new to Objective-C. I have written a function that returns two values. Now I would like to print it into two separate labels, how I can do it?
-(NSString *)abc:(NSInteger)weeks year:(NSInteger)year{
............
return ca , da ;
}
and when I call this function like
resultLabel1.text = [self abc year:year]; //output show the value of da
now I want to show the value of ca into resultLabel1.text and da into resultLabel2.text
is it possible?
You can only return a single value from any method in C and C-derived languages. So you simply need to return a single value that represents both values. You can achieve this by making use of a NSDictionary.
So make it:
-(NSDictionary *)abc:(NSInteger)weeks year:(NSInteger)year{
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
ca, #"object1",
da, #"object2", nil];
return dict;
}
Another way is to return an NSArray:
- (NSArray *)abc:(NSInteger)weeks year:(NSInteger)year {
NSArray *myArray = [NSArray arrayWithObjects:da, ca, nil];
return myArray;
}
And you can then use these values as:
NSArray *myArray = [self abc:2 year:2004];
textLabel.text = (NSString *)[myArray objectAtIndex:0];
textLabel2.text = (NSString *)[myArray objectAtIndex:1];
As Jules points out a method can "return" only a single value. However, you have several options for returning multiple values:
Return a pointer to an object, where the object contains multiple values. The object can be an NSArray, NSDictionary or you own class. Jules answer gave some examples of this.
Pass multiple pointers in your parameters, and the method can store results in the object or variable pointed to. See example here.
Return a struct that has multiple fields. There's an example here.
I'd use a NSDictionary to return multiple values from a method. In the dictionary each value is named and referenced by a key. The keys in this example are "ca" and "da" and the values are both a short string of text.
-(NSDictionary *) abc: (NSInteger) weeks year:(NSInteger) year {
NSString* ca = [NSString stringWithFormat:#"Week is %d", weeks];
NSString* da = [NSString stringWithFormat:#"Year is %d", year];
return [[NSDictionary alloc] initWithObjectsAndKeys:ca, #"ca", da, #"da", nil];
}
Call the method and pick out the returned values with code like this:
NSInteger weekParam = #"52".integerValue;
NSInteger yearParam = #"2011".integerValue;
NSDictionary *result = [self abc:weekParam year:yearParam];
NSLog(#"ca has value: %#", [result objectForKey:#"ca"]);
NSLog(#"da has value: %#", [result objectForKey:#"da"]);
You log should have the following lines added:
ca has value: Week is 52
da has value: Year is 2011
You can "return" multiple objects as parameters in a block:
- (void)method {
[self returnMultipleObjectsWithCompletion:^(NSString *firstString, NSString *secondString) {
NSLog(#"%# %#", firstString, secondString);
}];
}
- (void)returnMultipleObjectsWithCompletion:(void (^)(NSString *firstString, NSString *secondString))completion {
if (completion) {
completion(#"firstReturnString", #"secondReturnString");
}
}
You will have to return an NSArray or NSDictionary with the two values.
I have and array of many strings.
I wan't to sort them into a dictionary, so all strings starting the same letter go into one array and then the array becomes the value for a key; the key would be the letter with which all the words in it's value's array begin.
Example
Key = "A" >> Value = "array = apple, animal, alphabet, abc ..."
Key = "B" >> Value = "array = bat, ball, banana ..."
How can I do that?
Thanks a lot in advance!
NSArray *list = [NSArray arrayWithObjects:#"apple, animal, bat, ball", nil];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
for (NSString *word in list) {
NSString *firstLetter = [[word substringToIndex:1] uppercaseString];
NSMutableArray *letterList = [dict objectForKey:firstLetter];
if (!letterList) {
letterList = [NSMutableArray array];
[dict setObject:letterList forKey:firstLetter];
}
[letterList addObject:word];
}
NSLog(#"%#", dict);
You can achieve what you want through the following steps:
Create an empty but mutable dictionary.
Get the first character.
If a key for that character does not exist, create it.
Add the word to the value of the key (should be an NSMutableArray).
Repeat step #2 for all keys.
Here is the Objective-C code for these steps. Note that I am assuming that you want the keys to be case insensitive.
// create our dummy dataset
NSArray * wordArray = [NSArray arrayWithObjects:#"Apple",
#"Pickle", #"Monkey", #"Taco",
#"arsenal", #"punch", #"twitch",
#"mushy", nil];
// setup a dictionary
NSMutableDictionary * wordDictionary = [[NSMutableDictionary alloc] init];
for (NSString * word in wordArray) {
// remove uppercaseString if you wish to keys case sensitive.
NSString * letter = [[word substringWithRange:NSMakeRange(0, 1)] uppercaseString];
NSMutableArray * array = [wordDictionary objectForKey:letter];
if (!array) {
// the key doesn't exist, so we will create it.
[wordDictionary setObject:(array = [NSMutableArray array]) forKey:letter];
}
[array addObject:word];
}
NSLog(#"Word dictionary: %#", wordDictionary);
Take a look at this topic, they solves almost the same problem as you — filtering NSArray into a new NSArray in objective-c Let me know if it does not help so I will write for you one more code sample.
Use this to sort the contents of array in alphabetical order, further you design to the requirement
[keywordListArr sortUsingSelector:#selector(localizedCaseInsensitiveCompare:)];
I just wrote this sample. It looks simple and does what you need.
NSArray *names = [NSArray arrayWithObjects:#"Anna", #"Antony", #"Jack", #"John", #"Nikita", #"Mark", #"Matthew", nil];
NSString *alphabet = #"ABCDEFGHIJKLMNOPQRSTUWXYZ";
NSMutableDictionary *sortedNames = [NSMutableDictionary dictionary];
for(int characterIndex = 0; characterIndex < 25; characterIndex++) {
NSString *alphabetCharacter = [alphabet substringWithRange:NSMakeRange(characterIndex, 1)];
NSArray *filteredNames = [names filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF BEGINSWITH[C] %#", alphabetCharacter]];
[sortedNames setObject:filteredNames forKey:alphabetCharacter];
}
//Just for testing purposes let's take a look into our sorted data
for(NSString *key in sortedNames) {
for(NSString *value in [sortedNames valueForKey:key]) {
NSLog(#"%#:%#", key, value);
}
}