Objective-Cでnsmutablearrayを動的に並べ替える方法は?
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10-10-2019 - |
質問
SQLiteテーブルから行を取得し、オブジェクトを動的に作成し、NSMutableArrayにオブジェクトを追加しています。私の問題は、距離属性に基づいて配列内のオブジェクトを動的に並べ替える方法を理解できないことです(これはダブルです)。最大。
私の関連するコードは次のようになります:
sqlite3 *database;
//Init the restaurant array
restaurants = [[NSMutableArray alloc] init];
CLLocation *firstLocation = [[[CLLocation alloc] initWithLatitude:userLatitude longitude:userLongitude] autorelease];
//Open the database from the users filesystem
if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) {
//setup the SQL statement and compile it for faster access
const char *sqlStatement = "select * from restaurant";
sqlite3_stmt *compiledStatement;
if (sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) {
//loop through the results and add them to the feeds array
while (sqlite3_step(compiledStatement) == SQLITE_ROW) {
//read the data from the result row
NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
NSString *aAddress = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)];
NSString *aCity = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 3)];
NSString *aProvinceState = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 4)];
NSString *aPostalZipCode = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 5)];
NSString *aCountry = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 6)];
NSString *aPhoneNumber = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 7)];
NSString *aHours = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 8)];
double aLat = sqlite3_column_double(compiledStatement, 9);
double aLon = sqlite3_column_double(compiledStatement, 10);
CLLocation *secondLocation = [[[CLLocation alloc] initWithLatitude:aLat longitude:aLon] autorelease];
CLLocationDistance restDistance = [secondLocation distanceFromLocation:firstLocation];
CLLocationDistance distanceKm = restDistance / 1000.0;
NSString *aDist = [[NSString alloc] initWithFormat: @"%f", distanceKm];
Restaurant *restaurant = [[Restaurant alloc] initWithName:aName address:aAddress city:aCity provinceState:aProvinceState postalZipCode:aPostalZipCode country:aCountry phoneNumber:aPhoneNumber hours:aHours latitude:aLat longitude:aLon distance:aDist];
//add the restaurant object to the restaurant array
[restaurants addObject:restaurant];
[restaurant release];
}
}
sqlite3_finalize(compiledStatement);
}
sqlite3_close(database);
}
この機能がコースを終了すると、レストランアレイは、最も近く(最小距離の2倍の値)順に(最大距離の2倍の値)順にあるレストランオブジェクトを含むソートアレイである必要があります。
解決
nsmutablearrayのsortusingselectorを使用して、レストランオブジェクトの比較関数を呼び出します。
@implementation Restaurant
- (double) distance { return _distance; }
- (NSComparisonResult) compareDistance:(Restaurant *) iRHS {
double lhs, rhs;
lhs = [self distance];
rhs = [iRHS distance];
if ( lhs < rhs ) return NSOrderedAscending;
if ( lhs > rhs ) return NSOrderedDescending;
return NSOrderedSame;
}
@end
...
[restaurants sortUsingSelector: @selector(compareDistance:)];
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