使用NSPredicate过滤数组

Question

我有一个叫做“SMessage”的类；

@interface SMessage:NSObject
@property(nonatomic)int messageId;
@end

我还可以创建一个名为SDay的类；SDay可以有很多消息(SMessage)；

@interface SDay:NSObject
@property(nonatomic, strong)NSMutableArray *messages;
@end

在期末考试中，我有一个普通的类，其中我有几天数组；

@interface SCommonClass:NSObject 
@property(nonatomic, strong)NSMutableArray *days;
@end

我尝试过滤天数组，并找到messageId =100的邮件(例如)；

我不知道如何使用NSPredicate来做到这一点；谢谢你的回答；

Answer 1

NSPredicate *p = [NSPredicate predicateWithBlock:^BOOL(id object, NSDictionary *bindings) {

    SDay* day = (SDay*)object;
    NSMutableArray* messages = day.messages;
    NSPredicate* predicate = [NSPredicate predicateWithFormat:@"messageId == 100"];

    if ([messages filteredArrayUsingPredicate:predicate].count == 0) {
        return NO;
    }
    else{
        return YES;
    }

}];


NSArray* result = [common.days filteredArrayUsingPredicate:p];

============update===============

NSPredicate *p = [NSPredicate predicateWithBlock:^BOOL(id object, NSDictionary *bindings) {

    SDay* day = (SDay*)object;
    NSMutableArray* messages = day.messages;
    NSPredicate* predicate = [NSPredicate predicateWithFormat:@"messageID == 100"];
    NSArray *filteredMessages = [messages filteredArrayUsingPredicate:predicate];
    if (filteredMessages.count == 0) {
        return NO;
    }
    else{
        day.messages = [NSMutableArray arrayWithArray:filteredMessages];
        return YES;
    }

}];