Parse NSString with colons into NSDictionary - ios

Question

I'm trying to parse a string I have that follows the format below
Key: Object\n
Key: Object\n
Key: Object\n
Into an NSDictionary so that it is more easily accessible to me. My question is: Is there a better way to do this that is already incorporated into obj-c? My first thought would be to form an array based on the separation of the : and the newlines and then use the even values as the keys and the odd values as the objects but that seems a little overcomplicated.

Answer 1

NSString *str = #"Key1: Object1\nKey2: Object2\nKey3: Object3\n";
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
NSArray *lines = [str componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
for (NSString *aKeyValue in lines)
{
NSArray *components = [aKeyValue componentsSeparatedByString:#":"];
if ([components count] != 2) continue; //Bypass stranges lines, like the last one
NSString *key = [components[0] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
NSString *value = [components[1] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
[dict setObject:value forKey:key];
}
NSLog(#"Dict:\n%#", dict);
This gives:
$> Dict:
{
Key1 = Object1;
Key2 = Object2;
Key3 = Object3;
}
Note: I had to rename your String with different keys, because they need to be unique (else, it would have replace the value keeping only the last one). If it's not the case, you maybe don't want a NSDictionary.

Answer 2

This code should work (in Swift):
func parseString(_ str: String) -> Dictionary<String, String> {
let lines = str.components(separatedBy: .newlines)
var dict = [String: String]()
for line in lines {
let list = line.components(separatedBy: ": ")
if list.count == 2 {
dict[list[0]] = list[1]
}
}
return dict
}
First, we create an array with the lines, then for each line, we extract key and value separated by the colon.

Answer 3

All the solutions offered at the time of writing create an array of lines and then process those lines. NSString provides the method enumerateLinesUsingBlock: to avoid creating this intermediate array of lines. Assuming your string is referenced by the variable str then:
NSMutableDictionary *results = [NSMutableDictionary new];
[str enumerateLinesUsingBlock:^(NSString *line, BOOL *stop)
{
NSArray<NSString *> *kvPair = [line componentsSeparatedByString:#":"]; // split key & value
if (kvPair.count != 2) return; // ignore any line not matching "key : value"
NSString *key = [kvPair[0] stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceCharacterSet]; // remove any whitespace
NSString *value = [kvPair[1] stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceCharacterSet];
results[key] = value;
}];
will produce the dictionary in results.
Note: The stop parameter passed to the block is to allow the line enumeration to be terminated early, it is not used in this sample. However if a malformed line is found it could be used to terminate the parsing early.

Answer 4

There is no better way to do this with Objective C. Here is how you could approach this. Separate strings by new line character, then again break each line strings with ":", put left part to key and right part to value.
NSString *string = #"name: Jack Johnson\n\
address: Australia\n\
interest: Singing\n\";
NSString *trimmedString = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSArray *keyValuePairs = [trimmedString componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
for (NSString *keyValuePair in keyValuePairs) {
NSArray *keyValues = [keyValuePair componentsSeparatedByString:#":"];
dict[[keyValues.firstObject stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]] = [keyValues.lastObject stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
}
NSLog(#"%#", dict);
Something like this. But this gets pretty nice with swift like so,
let keyValueTuple = string.trimmingCharacters(in: .whitespacesAndNewlines)
.components(separatedBy: .newlines)
.map { line -> (String, String) in
let keyValuePairs = line.components(separatedBy: CharacterSet(charactersIn: ":"))
let key = keyValuePairs.first!.trimmingCharacters(in: .whitespaces)
let value = keyValuePairs.last!.trimmingCharacters(in: .whitespaces)
return (key, value)
}
let dict = Dictionary(uniqueKeysWithValues: keyValueTuple)