如何排序NSMutableArray元素？

Question

我有一個包含NSString's-模型類studentName ， studentRank和studentImage 。 我想根據studentRanks對NSMutableArray進行studentRanks 。 我所做的是

- (void)uploadFinished:(ASIHTTPRequest *)theRequest
{
    NSString *response = nil;
    response = [formDataRequest responseString];
    NSError *jsonError = nil;
    SBJsonParser *json = [[SBJsonParser new] autorelease];
    NSArray *arrResponse = (NSArray *)[json objectWithString:response error:&jsonError];
    if ([jsonError code]==0) {
        // get the array of "results" from the feed and cast to NSArray
        NSMutableArray *localObjects = [[[NSMutableArray alloc] init] autorelease];
        // loop over all the results objects and print their names
        int ndx;

        for (ndx = 0; ndx < arrResponse.count; ndx++) 
        {
            [localObjects addObject:(NSDictionary *)[arrResponse objectAtIndex:ndx]];
        }

        for (int x=0; x<[localObjects count]; x++) 
        {
            TopStudents *object = [[[TopStudents alloc] initWithjsonResultDictionary:[localObjects objectAtIndex:x]] autorelease];

            [localObjects replaceObjectAtIndex:x withObject:object];
        }

        topStudentsArray = [[NSMutableArray alloc] initWithArray:localObjects];

    }
}

如何根據學生得分的排名對topStudentsArray進行排序，如果兩個或多個學生的排名相同，如何對它們進行分組。 我確實喜歡這個

TopStudents *object;
    NSSortDescriptor * sortByRank = [[[NSSortDescriptor alloc] initWithKey:@"studentRank" ascending:NO] autorelease];
    NSArray * descriptors = [NSArray arrayWithObject:sortByRank];
    NSArray * sorted = [topStudentsArray sortedArrayUsingDescriptors:descriptors];

但這不能正確顯示結果。 請幫助我克服這個問題。 提前致謝。

Answer 1

做這樣的事情可能會解決問題

Initially sort the arrGroupedStudents in the (ascending/descending) order of studentRank

//Create an array to hold groups
NSMutableArray* arrGroupedStudents = [[NSMutableArray alloc] initWithCapacity:[topStudentsArray count]];

for (int i = 0; i < [topStudentsArray count]; i++) 
{
    //Grab first student
    TopStudents* firstStudent = [topStudentsArray objectAtIndex:i];

    //Create an array and add first student in this array
    NSMutableArray* currentGroupArray = [[[NSMutableArray alloc] initWithCapacity:0] autorelease];
    [currentGroupArray addObject:firstStudent];

    //create a Flag and set to NO
    BOOL flag = NO;
    for (int j = i+1; j < [topStudentsArray count]; j++) 
    {
        //Grab next student
        TopStudents* nextStudent = [topStudentsArray objectAtIndex:j];  

        //Compare the ranks
        if ([firstStudent.studentRank intValue] == [nextStudent.studentRank intValue]) 
        {
            //if they match add this to same group
            [currentGroupArray addObject:nextStudent];
        }
        else {
            //we have got our group so stop next iterations
            [arrGroupedStudents addObject:currentGroupArray];
                           // We will assign j-1 to i
            i=j-1;
            flag = YES;
            break;
        }
    }
    //if entire array has students with same rank we need to add it to grouped array in the end
    if (!flag) {
        [arrGroupedStudents addObject:currentGroupArray];
    }
}

最后，您的arrGroupedStudents將包含等級相等的分組數組。 我尚未測試運行代碼，因此您可能需要修復一些不適當的內容。 希望能幫助到你

Answer 2

如果要按等級順序顯示，則應將ascending設置為YES 。

NSSortDescriptor * sortByRank = [[NSSortDescriptor alloc] initWithKey:@"studentRank" ascending:YES];

Answer 3

static int mySortFunc(NSDictionary *dico1, NSDictionary *dico2, void *context)
{
    NSString *studentName1 = [dico1 objectForKey:@"studentName"];
    NSString *studentName2 = [dico2 objectForKey:@"studentName"];
    return [studentName1 compare:studentName2];
}

- (IBAction)sortBtnTouched:(id)sender
{
    [topStudentsArray sortUsingFunction:mySortFunc context:NULL];
}