Iterar over array of entity and get value of some key based on value of “other key” matche

问题

I have an array of entity class (eg SubmittedAnswer). Its JSON format is look like as below.

{
"submittedAnswers": [{
    "submittedQuestionId": "C7B3C4BE-CC3C-438F-A118-E798884A5FE0",
    "serialNumber": 4,
    "option": " it has a very large mass.",
    "testQuestionId": "55230160-b905-47d5-a91c-e1dda6dd0634",
}, {
    "submittedQuestionId": "9A6E9EA8-1BC0-4ED9-81E8-28B7E554D5E0",
    "serialNumber": 1,
    "option": " downward",
    "testQuestionId": "fd0b3ae0-e999-48a6-89b8-a89b02e7b793",
}]

}

I want to find "option" field from that array whose "submittedQuestionId" is "something....". I dont want to use for loop. Currently i am using following code.

NSString *submittedQuestionId = "something...."
int index    = [[submittedAnswers valueForKey:@"submittedQuestionId"] indexOfObject:submittedQuestionId];
NSString *option = [[submittedAnswers valueForKey:@"option"] objectAtIndex:index];

I need better solution for this problem.

回答1:

Assuming that submittedAnswers is an NSArray of NSDictionary objects, I found the answer here: Stack Overflow > iPhone - Searching NSArray of NSDictionary objects

// Array `submittedAnswers` of sample data
NSArray* submittedAnswers = @[
@{
@"submittedQuestionId" : @"C7B3C4BE-CC3C-438F-A118-E798884A5FE0" ,
@"serialNumber" : @4 ,
@"option" : @" it has a very large mass." ,
@"testQuestionId" : @"55230160-b905-47d5-a91c-e1dda6dd0634" } ,
@{
@"submittedQuestionId" : @"9A6E9EA8-1BC0-4ED9-81E8-28B7E554D5E0" ,
@"serialNumber" : @1 ,
@"option" : @" downward" ,
@"testQuestionId" : @"fd0b3ae0-e999-48a6-89b8-a89b02e7b793" } ] ;


NSString *submittedQuestionId = @"9A6E9EA8-1BC0-4ED9-81E8-28B7E554D5E0" ;
NSPredicate* predicate = [NSPredicate predicateWithFormat:@"submittedQuestionId = %@", submittedQuestionId] ;
NSArray* foundQuestions = [submittedAnswers filteredArrayUsingPredicate:predicate] ;
NSDictionary* foundQuestion = foundQuestions[0] ;

回答2:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"submittedQuestionId == %@", yourSubmittedQuestionId];
NSArray *filteredArray = [myArray filteredArrayUsingPredicate:predicate];
id firstFoundObject = nil;
if ([filteredArray count] > 0) {
    firstFoundObject = [filteredArray objectAtIndex:0];
}

Please make sure your SubmittedAnswer class has property submittedQuestionId

来源：https://stackoverflow.com/questions/13975702/iterar-over-array-of-entity-and-get-value-of-some-key-based-on-value-of-other-k

标签

objective-c

nsarray