NSDictionary *story = [stories objectAtIndex: indexPath.row];
cell.text=[NSString stringwithFormat:[story objectForKey#"message];
i dont knw what exaclty "message " contains (what is the meaning of objectForKey#"message")
EDIT CODE
NSString *key =[appDelegate.books objectAtIndex:indexPath.row];
//dict y=#"Name";
NSArray *nameSection = [dict objectForKey:key];
NSDictionary *story = [nameSection objectAtIndex: indexPath.row];
cell.text=[NSString stringwithFormat:[story objectForKey:key]];
NSLog(#"Value Of message: %#", [dict objectForKey:key]);
why my code crashes
If you are more familiar with Java or C# the code is equivalent to something like this:
// Assuming stories is declared as: List<Dictionary<string, string> stories;
Dictionary<string, string> story = stories[indexPath.row];
cell.Text = String.Format(story["message"]);
In Smalltalk-style (and therefore Objective-C too) Object Oriented programming, methods are more like messages to other objects. So a good Objective-C method name should read like an English sentence (Subject-Verb-Object). Because of this working with dictionaries (hash tables) looks like this:
[myDictionary setObject:#"Value" forKey:#"someKey"];
[myDictionary objectForKey:#"someKey"]; // == #"Value"
In Java it would be:
myDictionary.put("someKey", "Value");
myDictionary.get("someKey"); // == "Value"
Notice how the key ("someKey") was the first argument in the Java example. In Objective-C you name your arguments with the method name, hence setObject: forKey:. Also notice that in Objective-C strings start with an # symbol. That's because Objective-C strings are different from regular C strings. When using Objective-C you almost always use Objective-C's # strings.
In C# there is a special syntax for Dictionaries so it becomes:
myDictionary["someKey"] = "Value";
myDictionary["someKey"]; // == "Value"
One important problem that you might encounter if you're new is the problem of native types.
In Java to add an int to a Dictionary you used to have to do:
myDictionary.put("someKey", new Integer(10));
Because the primitive types (int, char/short, byte, boolean) aren't real Objects. Objective-C has this problem too. So if you want to put an int into a dictionary you must use NSNumber like so:
[myDictionary setObject:[NSNumber numberForInt:10]
forKey:#"someKey"];
And you pull out the integer like so:
NSNumber *number = [myDictionary objectForKey:#"someKey"];
[number intValue]; // == 10
EDIT:
Your code might be crashing if you have a '%' character in your string, since stringWithFormat is just like NSLog in that it takes many arguments. So if story["message"] is "Hello" then it'll work fine without extra arguments but if it's "Hello %#" you need to add one argument to stringWithFormat.
NSString *message = #"Hello %#";
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:message forKey:#"message"];
NSString *output = [NSString stringWithFormat:[dict objectForKey:#"message"], #"World!"];
// output is now #"Hello World!".
#"message" is a key for a value stored in the NSDictionary object. The first line declares an NSDictionary named story that appears to come from an array.
If you want to find what value is stored for the key:#"message", consider using:
NSLog(#"Value Of message: %#", cell.text);
Run and check the console to see the output. (SHIFT + COMMAND + Y) in XCode will bring up the console, if that's what you are using. If you are unfamiliar with NSArrays/NSDictionaries, give Apple's Documentation a look.
I'm just guessing at all of this since that is a very limited sample of code. Try submit more code when you ask a question so that the viewers can get a better idea of your questions.
That is an example of key-value coding, and a lot of information is available on the Apple dev site if you're interested:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/KeyValueCoding/KeyValueCoding.html
Related
I'm working on a project and I want to be able to handle some template type messages. The template would contain something like:
"{{user1}} has just created an account"
I then have a data map that would give you a location within the NSMutableDictionary where the data is located:
"activity.message.status"
I then want to be able to query the NSMutableDictionary by splitting up that string, so that it becomes something like:
[[[myDictionary objectForKey:#"activity"] objectForKey:#"message"] objectForKey:#"status"]
I could make something as long as it was consistant on being just 3 strings, but some may be more or less.
Any help would be extremely appreciated.
It's actually much easier than splitting strings into keys. Apples Key-Value-Coding allows exactly what you want.
[myDictionary valueForKeyPath:#"activity.message.status"];
A key path is a string of dot separated keys that is used to specify a sequence of object properties to traverse. The property of the first key in the sequence is relative to the receiver, and each subsequent key is evaluated relative to the value of the previous property.
For example, the key path address.street would get the value of the address property from the receiving object, and then determine the street property relative to the address object.
Key-Value Coding Programming Guide
You would do something like,
NSArray *array = [#"activity.message.status" componentsSeperatedByString:#"."];
Which will create an array containing {activity,message,status).
Now you have your array you can use for querying your dictionary.
[[[myDictionary objectForKey:[array objectAtIndex:0]] objectForKey:[array objectAtIndex:1]] objectForKey:[array objectAtIndex:2]];
Which is equivalent to:
[[[myDictionary objectForKey:#"activity"] objectForKey:#"message"] objectForKey:#"status"];
Hope this helps !
It's not clear to me from your question how we should map user1 to activity.message.status. For now I'll assume you mean that the template might contain a string like "{{activity.message.status}}" and you want to be able to parse that.
Here's one iteration that operates on an NSMutableString that can be looped until no match is found:
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"\\{\\{.+?\\}\\}"
options:NSRegularExpressionCaseInsensitive
error:&error];
NSRange matchRange = [regex rangeOfFirstMatchInString:string
options:0 range:NSMakeRange(0, [string length])];
NSRange keyPathRange = NSMakeRange(matchRange.location + 2, matchRange.length - 4);
NSString *keyPath = [string substringWithRange:keyPathRange];
NSString *newSubstring = [myDictionary valueForKeyPath:keyPath];
[string replaceCharactersInRange:matchRange withString:newSubstring];
I haven't tested this code.
How about a (recursive ... cool) category method on NSMutableDictionary like this:
- (void)setObject:(id)object forCompoundKey:(NSString *)compoundKey {
NSArray *keys = [compoundKey componentsSeparatedByString:#"."];
if ([keys count] == 1) {
return [self setObject:object forKey:compoundKey];
}
// get the first component of the key
NSString *key = [keys objectAtIndex:0];
// build the remaining key with the remaining components
NSRange nextKeyRange;
nextKeyRange.location = 1;
nextKeyRange.length = [keys count] - 1;
NSArray nextKeys = [keys subarrayWithRange:nextRange];
NSString *nextKey = [nextKeys componentsJoinedByString:#"."];
NSMutableDictionary *nextDictionary = [NSMutableDictionary dictionary];
[self addObject:nextDictionary forKey:key];
// now the cool part... recursion
[nextDictionary setObject:object forCompoundKey:nextKey];
}
I haven't tested this, but it passes a quick desk check. The objectForCompoundKey: retrieval can be written analogously.
Hey guys :) I am quite new to stack overflow and iPhone programming. I am trying to parse a complex JSON to display some stuff in the UITableView.
a part of the JSON structure -
{"1":{"1":"Ent1","done":"No"},"2":{"1":"Ent2","done":"No"}}
I am able to parse through the main keys "1" and "2" and able to grab the values corresponding to the key "1" inside {"1":"Ent1","done":"No"}, {"1":"Ent2","done":"No"} store them into a dictionary/ a string with the following code :
for (NSString *key in dict)
{
NSString *answer = [dict objectForKey:#"1"];
NSLog(#"%#", answer);
}
The result is Ent1 and Ent2 because the code iterates over the for loop and checks for the objects with key "1".
The problem is this - I want to store both the values(Ent1 and Ent2) into an array.
I use the following code:
NSMutableArray *array = [[NSMutableArray alloc] initWithObjects: answer, nil];
but it just takes the last index in the dictionary which is Ent2.
Could you please tell me how could I add both the values for key 1 into an array?
Thanks in advance :)
To add to jamapag's answer, you can also use JSON libraries in objective C which do all the work for you like SBJSON or YAJL, or even as part of the more recent versions of the mac/iOS SDKs, NSJSONSerialization.
NSMutableArray *array = [[NSMutableArray alloc] init];
for (NSString *key in dict)
{
NSString *answer = [dict objectForKey:key];
[array addObject:answer];
}
How would I filter through an array and return values that contain a certain part of a string? I have a text box where, for the sake of this example, a user puts in 25, and then hits a "Done" button.
Example:
Original Array {25-1002, 25-1005, 12-1003, 1000-0942, 1-1, 234-25}
I want it to return (after sorting through it and pulling the values I want):
New Array {25-1002, 25-1005}
Please note that in the original array, the last value of 234-25 has a 25 in it as well but is not pulled through. It needs to be the number on the first part of the hyphen.
Thanks in advance!
Use the -filteredArrayUsingPredicate: method, like this:
NSString *searchText = [someField.text stringByAppendingString:#"-"];
newArray = [originalArray filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^(NSString *value, NSDictionary *bindings){
return ([value rangeOfString:searchText].location != NSNotFound)
}]];
Note that blocks (the ^{} thing) aren’t available pre-iOS 4, so you’ll have to use another of NSPredicate’s constructors if you’re targeting 3.x devices as well.
as an easy to understand answer (not using NSPredicate, which can be intimidating (but is really the correct way to do it)):
NSMutableArray *myNewArray = [[NSMutableArray alloc] init];
for (NSString *string in myArray) {
if([[string substringToIndex:3] isEqualToString #"25-"])
{
[myNewArray addObject:string];
}
}
i'm new in the iphone and json world . i have this json structure . You can see it clearly by putting it here http://jsonviewer.stack.hu/ .
{"#uri":"http://localhost:8080/RESTful/resources/prom/","promotion":[{"#uri":"http://localhost:8080/RESTful/resources/prom/1/","descrip":"description
here","keyid":"1","name":"The first
name bla bla
","url":"http://localhost/10.png"},{"#uri":"http://localhost:8080/RESTful/resources/promo/2/","descrip":"description
here","keyid":"2","name":"hello","url":"http://localhost/11.png"}]}
i want to parse it with json-framework . I tried this
NSDictionary *json = [myJSON JSONValue];
NSDictionary *promotionDic = [json objectForKey:#"promotion"];
NSLog(#" res %# : ",[promotionDic objectAtIndex:0]);
But then how to do to get for exemple , the name of the object at index 0 ? I think i should put object in an NSArray ? but i dont find how :/ and i dont the number of object is variable . Help please .
First off, You need this line after you load the JSON
NSLog(#" json %# : ",[json description]);
That will tell you what you have.
Secondly, you can't call objectAtIndex: on a dictionary. If it works, its because promotionDict is really an NSArray. (The NSLog will tell you). In Objective - C you can assign to any kind of pointer, which is confusing to new developers, but is part of the language, and really is a feature.
With an NSArray you can ask for the number of things in it, [myArray count], etc. You need to command double click in XCode to open up the docs for NSDictionary, etc.
The JSON says:
..."promotion":[{"#u...
That "[" there means that "promotion" is keyed to an array, not a dictionary.
So really your code should be:
NSDictionary *json = [myJSON JSONValue];
NSArray *promotions = [json objectForKey:#"promotion"];
NSLog(#"res: %#",[promotions objectAtIndex:0]);
//COPY THIS CODE IN A FRESH PROJECT!!!
//THIS 2 LINES ARE JUST EXAMPLES, OF VALUES PUSHES OUT A DATABASE
NSString *messagelevel1 = #"45";
NSString *currentlevel = #"1";
NSString *HuidigLevel = currentlevel;
NSDecimalNumber *huidigleveldec = [[NSDecimalNumber alloc] initWithString: HuidigLevel];
float HuidigLevelRek = [huidigleveldec floatValue];
//HERE IS THE PROBLEM
NSString* LevelTotaal=[[NSString alloc] initWithFormat:#"messagelevel%.f",HuidigLevelRek];
NSString*result = LevelTotaal;
NSLog(#"%#",result);
// THE ABOVE RESULT SHOULD RETURN THE SAME VALUE AS THE NEXT (messagelevel1) LINE BUT IT RETURNS ONLY "messagelevel1" AND NOT THE VALUE!
NSLog(#"%#",messagelevel1);
I want the *result string behaves like the *huidiglevel string and fetch some information, but because the LevelTotaal is a NSString, It doesn't fetch this information. I really got no idea where to google for this problem, searching the Developer docs didn't helped either . Maybe you guys can help me out?
Actually the second NSLog returns the value and to first NSLog just returns messagelevel1. To tell you in short ;)
I hope you guys get what I'm saying!
I think what you're trying to do is use variable variables, a system that does not exist in Objective-C. In PHP, you can use variable variables:
$hello = 'abcdef';
$varName = 'hello';
print $$varName; // prints the value of $hello, which is 'abcdef'
Like many things in PHP, this is not really a good way to design software. Instead, consider using something like a NSDictionary, this allows you to give specific data a key.
NSMutableDictionary *aDict = [NSMutableDictionary dictionary];
[aDict setObject:[NSNumber numberWithFloat:4.5] forKey:#"messageLevel1"];
NSString *result = [aDict objectForKey:#"messageLevel1"];
You can obtain the data dynamically, the key can be generated or obtained at runtime.
Edit:
Rather than having variables called messageLevel1, messageLevel2, messageLevel3 ... messageLeveln, just use an array.
NSMutableArray *messageLevels = [NSMutableArray array];
[messageLevels addObject:#"1"];
[messageLevels addObject:#"45"];
[messageLevels addObject:#"123"];
NSString *result = [messageLevels objectAtIndex:HuidigLevelRek];