iOS开发之Realm数据库的简单使用

1.安装

Realm github下载地址

如果使用cocoapods,示例语句如下
platform :ios, '8.0'
target 'Simona_Realm' do
pod 'Realm', '~> 3.0.0-beta.3'
end

2.创建简易模型,继承于RLMObject,存储在数据库的模型都需要继承于RLMObject

Person.h
#import <Realm/Realm.h>
RLM_ARRAY_TYPE(Person);
@interface Person : RLMObject

@property NSString *personId;
@property BOOL status;
@property NSString *sex;

@end

Person.m
#import "Person.h"

@implementation Person

// 设置主键,确保数据唯一性
+ (NSString *)primaryKey {
    return @"personId";
}

// 设置属性不为nil
+ (NSArray<NSString *> *)requiredProperties {
    return @[@"sex"];
}

// 设置忽略属性
+ (NSArray<NSString *> *)ignoredProperties {
    return @[];
}

// 设置默认值,对于不为null的属性,默认给空
+ (NSDictionary *)defaultPropertyValues {
    return @{@"sex":@""};
}

//索引属性,主要用于搜索,根据性别进行搜索
+ (NSArray<NSString *> *)indexedProperties {
    return @[@"sex",@"woman"];
}

@end

关于RLMObject
1.Realm忽略了OC的属性特性(如nonatomic, atomic, strong,retain, weak,copy等),所以在声明属性时可不写,，这些特性会一直生效直到被写入数据库。
2.Realm支持以下的类型BOOL, NSInteger, long, double, CGFloat, NSString, NSDate, NSData等
3.定义了RLM_ARRAY_TYPE(Person)表示支持RLMArray属性,相当于允许RLMArray<Person>属性的使用,例如:在其他属性里可@property RLMArray<Person *><Person> *personal如此使用,相当于继承关系(本文暂不做赘述)

3.使用

<1.>存储

模拟存储一万条假数据 
RLMRealm *realm = [RLMRealm defaultRealm];
       [realm transactionWithBlock:^{
           for (int i = 0; i < 10000; i++) {
               Person *person = [[Person alloc]init];
               person.personId = [NSString stringWithFormat:@"张%d",i];
               person.sex = @"Not scanned";
               person.status = YES;
               [realm addObject:person];
           }
    }];

这里的
[realm transactionWithBlock:^{ }];
等同于
[realm beginWriteTransaction];
[realm commitWriteTransaction];
每次打开关闭数据库时都应执行此操作

<2.>删除

 RLMRealm *realm = [RLMRealm defaultRealm];
    [realm beginWriteTransaction];
    [realm deleteAllObjects];
    [realm commitWriteTransaction];

<3.>查询

1.根据谓词查询
// RLMResults相当于查询到的数组
NSPredicate *pred = [NSPredicate predicateWithFormat:@"status = %ld", NO];
RLMResults *result = [Person objectsWithPredicate:pred];
Person *per = result[indexPath.row];

2.根据条件查询
RLMResults *result = [Person objectsWhere:@"status = 'NO' AND personId BEGINSWITH '张1'"];
Person *per = result[indexPath.row];

3.查询所有
RLMResults *persons = [Person allObjects];
Person *per = persons[indexPath.row];

<4.>更新

1.更新数据里某一属性值
NSPredicate *pred = [NSPredicate predicateWithFormat:@"personId = %@", strScan];
RLMResults *result = [Person objectsWithPredicate:pred];
    if (result.count != 0) {

        RLMRealm *r = [RLMRealm defaultRealm];
        [r beginWriteTransaction];
        //直接修改
        Person *person = result[0];
        person.sex = @"Has been scanned";
        person.status = NO;
        [r commitWriteTransaction];
}

2.创建一个新值并更新数据库,createOrUpdateInRealm:通过主键来更新插入

 NSPredicate *pred = [NSPredicate predicateWithFormat:@"personId = %@", strScan];
    RLMResults *result = [Person objectsWithPredicate:pred];
    if (result.count != 0) {
        
        Person *person = [[Person alloc]init];
        person.personId = @"Simona1";
        person.sex = @"woman";
        person.status = NO;
        RLMRealm *r = [RLMRealm defaultRealm];
        [r beginWriteTransaction];
        [Person createOrUpdateInRealm:r withValue:person];
        [r commitWriteTransaction];