谓词技术的使用 NSPredicate

前言

在进行一些数据的筛选的时候经常使用到它。

例如： CoreData的数据查询、按照特定条件（日期）排序的数据、从数组进行数据查询等等。

正文

谓词技术的使用 NSPredicate （以一定的条件（特定日期）过滤maTemp数组，即进行大数据搜索。）

示例一，将含有日期属性的对象数组中，进行按照日期重新进行分组

使用谓词进行数据分组 （数组元素为 自定义类型）

//2.按照日期进行分组展示//     重新按照日期进行分组组织数据//     找出不重复的日期    /**  对象操作:     针对数组的情况     @distinctUnionOfObjects：返回指定属性去重后的值的数组     @unionOfObjects：返回指定属性的值的数组，不去重     属性的值不能为空，否则产生异常。*/    //1）取出日期分组     NSArray *arDistinct = [maTemp valueForKeyPath:@"@distinctUnionOfObjects.strDateCreated"];//maTemp是一些含有日期属性的对象集合    //2）构建排序规则NSComparator    NSComparator cmptr = ^(id obj1, id obj2){        NSString *strData1 = obj1;        NSString *strData2 = obj2;        NSComparisonResult ret = [strData1 compare:strData2];        return ret;    }; //     3）按数字从小到大进行排序(将最新的数据显示在前面)    NSArray  *arSorted = [arDistinct sortedArrayUsingComparator:cmptr];    arSorted = arSorted.reverseObjectEnumerator.allObjects;//顺序取反    NSPredicate *predicate = nil;//     4）按照日期进行分组    for (NSString *strDateCreated in arSorted)    {        predicate = [NSPredicate predicateWithFormat:@"strDateCreated == %@", strDateCreated];        NSArray *arFiltered = [maTemp filteredArrayUsingPredicate:predicate];//以一定的条件（特定日期）过滤maTemp数组，即进行大数据搜索。              OrderQueryGroupData *data = [OrderQueryGroupData alloc];        data.strDateCreated = strDateCreated;        data.maOrderData = [NSMutableArray arrayWithArray:arFiltered];        data.maOrderDataF = [IPOrderDataFrame frameListWith:data.maOrderData];        [self.maOrderQuery addObject:data];    }

示例代码二： 数据的过滤，城市搜索

城市搜索

  */    //方式二： 谓词技术的使用    searchText  = searchText.uppercaseString;    NSPredicate *predicate = [NSPredicate predicateWithFormat:@" pinYinHead.uppercaseString  contains %@ or  name.uppercaseString  contains %@  or pinYin.uppercaseString  contains %@ ",searchText,searchText,searchText];    return [_cityModels filteredArrayUsingPredicate:predicate];}//方式一。+ (NSArray *)searchcityModelsWithSeatchText:(NSString *)searchText{    NSMutableArray *array = [NSMutableArray array];    searchText = [searchText uppercaseString];    for (DKCityModel *obj in _cityModels) {        if ([obj.name.uppercaseString containsString:searchText] || [obj.pinYin.uppercaseString containsString:searchText] || [obj.pinYinHead.uppercaseString containsString:searchText]) {            [array addObject:obj];        }    }    return array;}

示例代码3:银行列表的过滤

多个过滤条件的拼接

#pragma mark - ********     //列表的银行过滤- (void)predicateBankList{    if ([Session Instance].arrOnlySupportBankList.count == 0) {        return;    }    NSMutableString *stringpredicate = [NSMutableString string] ;//    for (NSString *code in ) {//        if ([code isEqualToString:[Session Instance].arrOnlySupportBankList[0]]) {//            [stringpredicate appendFormat:@"  strBankNO ==  %@ ",code];//        }else {//            [stringpredicate appendFormat:@"  strBankNO ==  %@ ",code];//        }//    }    NSInteger count = [Session Instance].arrOnlySupportBankList.count;    for (int i = 0;  i<count;i++) {        if (count == 1) {            [stringpredicate appendFormat:@"  strBankNO ==  '%@' ",[Session Instance].arrOnlySupportBankList[i]];        }else if (count>1){            if (i == 0) {                [stringpredicate appendFormat:@"  strBankNO ==  '%@' ",[Session Instance].arrOnlySupportBankList[i]];            }else{                [stringpredicate appendFormat:@"or  strBankNO ==  '%@' ",[Session Instance].arrOnlySupportBankList[i]];            }        }    }    if ([stringpredicate isEqualToString:@"" ] ) {        return;    }    NSPredicate *predicate = [NSPredicate predicateWithFormat:stringpredicate];    self.bankListDepositCard = [NSMutableArray arrayWithArray:[ self.bankListDepositCard  filteredArrayUsingPredicate:predicate]];    self.bankListCreditCard = [NSMutableArray arrayWithArray:[ self.bankListCreditCard  filteredArrayUsingPredicate:predicate]];}

示例4: 字符串数组的过滤（数组元素为系统的自有类型）

字符串数组的过滤

/** BankInfoData 对象的 的银行卡编号是否包含在 arrOnlySupportBankList 银行卡编号数组中 @return bool */- (BOOL)isaBankSelectedEqualToBusinessBank:(KNData*)data{   NSArray *arrOnlySupportBankList=  [KNSession Instance].arrOnlySupportBankList;//kevin    NSArray *tmp = [NSArray array];    NSString *stringpredicate = [NSString stringWithFormat:@" self ==  '%@'",data.strBankNO];    NSPredicate *predicate = [NSPredicate predicateWithFormat:stringpredicate];    tmp = [NSMutableArray arrayWithArray:[  arrOnlySupportBankList filteredArrayUsingPredicate:predicate]];    if (tmp.count>0) {        return YES;    }else{        return NO;    }}

例子5: Core Data的数据查询

例子：保存未读消息

#pragma mark - 保存未读消息/** 先查询，在修改 */+ (void)saveMessageWithMessage:(IPMessageDetailData*)data{    if (data.messageId == nil || data == nil){        return;    }    NSManagedObjectContext *context = [IPMessageDataTool shareContext];    NSFetchRequest *request = [[NSFetchRequest alloc] init];    request.entity = [NSEntityDescription entityForName:@"KNMessage" inManagedObjectContext:context];    // 设置排序（按照messageId降序）    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"messageId" ascending:NO];    request.sortDescriptors = [NSArray arrayWithObject:sort];    // 设置条件过滤(搜索name中包含字符串"Itcast-1"的记录，注意：设置条件过滤时，数据库SQL语句中的%要用*来代替，所以%Itcast-1%应该写成*Itcast-1*)    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"messageId = %@  AND operateID = %@",data.messageId,[SessionMgr Instance].operateID];    request.predicate = predicate;    // 执行请求    //    request.fetchLimit = 50;    NSError *error = nil;    NSArray *objs = [context executeFetchRequest:request error:&error];    if (error) {        [NSException raise:@"查询错误" format:@"%@", [error localizedDescription]];    }    Message *tmpMessage;    if (objs.count>0) {        tmpMessage = objs[0];        return;    }else{        tmpMessage = [NSEntityDescription insertNewObjectForEntityForName:@"Message" inManagedObjectContext:context];    }    tmpMessage.messageExpiredTime = data.messageExpiredTime;    tmpMessage.messageIssueTime = data.messageIssueTime;    tmpMessage.messageId = data.messageId;    tmpMessage.messageTitle = data.messageTitle;    tmpMessage.operateID = [SessionMgr Instance].operateID;    tmpMessage.isRead = NO;    BOOL success = [context save:&error];    if (!success) {        [NSException raise:@"访问数据库错误" format:@"%@", [error localizedDescription]];    }}

使用谓词进行数据分组 （数组元素为 自定义类型）

NSPredicate* predicate = [NSPredicate predicateWithFormat:@"Style == %@", [[NSNumber numberWithInteger:type] description]];    NSArray *arFiltered = [  model.List filteredArrayUsingPredicate:predicate];//以一定的条件（特定日期）过滤maTemp数组，即进行大数据搜索。    model.List = [NSMutableArray arrayWithArray:arFiltered];    return model;