nsdictionary中按值搜索的元素

Question

I have nsdictionary which contains elements with following structure

name --> value

email--> key

I get value(of above structure) from user, now I want to search element in nsdictionary by value(entered by user) not by key, whether it is present in nsdictionary or not and also want to get index of that element if present.

How to do this?

Answer 1

The best to do so would propably be

- (NSArray *)allKeysForObject:(id)anObject

This method of NSDictionary gives you back all the keys having anObject as their value. If you only have each object once in the whole dictionary it will logically return an array with only one key in it.

Answer 2

NSArray * users = ...; //your array of NSDictionary objects
NSPredicate *filter = [NSPredicate predicateWithFormat:@"email = test@gmail.com"];
NSArray *filteredContacts = [contacts filteredArrayUsingPredicate:filter];

for more than one value of email, then use an OR in the predicate:

filter = [NSPredicate predicateWithFormat:@"contact_type = 42 OR contact_type = 23"];

Answer 3

The dictionary data structure has no 'order', so you'd have to search for your key by iterating the collection and looking for the desired value.

Example:

NSString *targetKey = nil;
NSArray *allKeys = [collection allKeys];
for (int i = 0; i < [allKeys count]; ++i) {
    NSString *key = [allKeys objectAtIndex:i];
    NSString *obj = [collection objectForKey:key];
    if ([obj isEqualToString:searchedString]) { // searchedString is what you're looking for
        targetKey = key;
        break;
    }
}

// check if key was found (not nil) & proceed
// ...

Answer 4

You can search the entered value in NSDictionary , but you can't get an index of value , as NSDictionary has no order of key value pair.

    NSArray *array = [yourDictionaryObject allValues];
    if ([array containsObject:@"userEnteredValue"]) {
       <#statements#>
    }

Answer 5

You need to iterate through the Dictionary for the keys has the Value of your need: Try this:

NSArray *keys= [json allKeys];
    for (NSString *keysV in keys){
        NSLog(@"Keys are %@", keysV);
    if([Your_Dict objectForKey: keysV] isEqual:@"string to Match"){
    //Do your stuff  here 
    }
}