iOS Coredata的基本使用

ios coredata的基本使用

coredata 管理类：nsmanagedobjectmodel、nspersistentstorecoordinator、nsmanagedobjectcontext。其中，nsmanagedobjectmodel是模型管理类，管理app中的数据模型；nspersistentstorecoordinator将model和持久化存储联系起来，并且将上下文（nsmanagedobjectcontext）与持久化存储联系起来，其实就是充当解析器。nsmanagedobjectcontext是上下文类，负责管理数据的获取、创建和保存等工作。

coreda创建

（1）创建工程时，勾选“use core data”选项

（2）在工程中选择新建文件，在新建文件界面选择新建“data model”, 点击next即可新建

-coredata创建数据模型
进入刚建好的数据库中，如下图点击“add entity”增加一个数据模型，双击该entity进行重命名。点击2，在数据表中增加一个属性，双击该属性进行重命名，并且指定type类型。

点击“style”，可以看到数据库中所有数据表的关系图。

注：ios8之后，nsmanagedobjectmodel对nsmanagedobject统一管理，不需要再次创建subclass，在使用时，直接引入#import “entity名称+coredataproperties.h”头文件即可。

-创建appdatamanager单例，管理数据表增删改查等基本操作。
（1）声明nsmanagedobjectcontext、nsmanagedobjectmodel、nspersistentstorecoordinator为实体变量，并实现初始化方法：

@interface appdatamanager() {
    nsmanagedobjectcontext *objcontext;
    nsmanagedobjectmodel *objmodel;
    nspersistentstorecoordinator *persistentcoordinator;
}

@end

static appdatamanager *sharedinstance = nil;

@implementation appdatamanager

+ (instancetype)sharedinstance {
    static dispatch_once_t oncetoken;
    dispatch_once(&oncetoken, ^{
        sharedinstance = [[appdatamanager alloc] init];
    });
    return sharedinstance;
}

- (instancetype)init {
    self = [super init];
    if (self) {
        [self createobjmodel];
        [self createpersistentcoordinator];
        [self createobjcontext];
    }
    return self;
}

- (void)createobjmodel {
    if (!objmodel) {
        objmodel = [nsmanagedobjectmodel mergedmodelfrombundles:nil];
    }
}

- (void)createpersistentcoordinator {
    if (persistentcoordinator != nil) {
        return;
    }
    persistentcoordinator = [[nspersistentstorecoordinator alloc] initwithmanagedobjectmodel:objmodel];
    nsstring *dir = nssearchpathfordirectoriesindomains(nsdocumentdirectory, nsuserdomainmask, yes).firstobject;
    nsstring *path = [dir stringbyappendingstring:@"coredatademo.db"];
    nsurl *storeurl = [nsurl fileurlwithpath:path];
    nserror *error = nil;
    [persistentcoordinator addpersistentstorewithtype:nssqlitestoretype configuration:nil url:storeurl options:nil error:&error];
    if (!error) {
        nslog(@"数据库打开成功");
    } else {
        nslog(@"数据库打开失败:%@", [error description]);
    }
}

- (void)createobjcontext {
    if (objcontext != nil) {
        return;
    }
    nspersistentstorecoordinator *coordinator = persistentcoordinator;
    if (coordinator == nil) {
        return;
    }
    objcontext = [[nsmanagedobjectcontext alloc] initwithconcurrencytype:nsmainqueueconcurrencytype];
    objcontext.persistentstorecoordinator = coordinator;
}

（2）增加数据

- (bool)addscore:(nsdictionary *)dic {
    nsfetchrequest *request = [nsfetchrequest fetchrequestwithentityname:@"score"];
    request.predicate = [nspredicate predicatewithformat:@"identity=%@", dic[@"identity"]];
    nserror *error = nil;
    nsarray *results = [objcontext executefetchrequest:request error:&error];
    if (error == nil) {
        nslog(@"score查询成功");
    } else {
        nslog(@"score查询失败%@", [error description]);
        return no;
    }
    score *score = nil;
    if (results && results.count > 0) {
        score = results.firstobject;
    } else {
        score = [nsentitydescription insertnewobjectforentityforname:@"score" inmanagedobjectcontext:objcontext];
    }
    score.name = dic[@"name"];
    score.identity = dic[@"identity"];
    score.score = dic[@"score"];
    [objcontext save:&error];
    if (error == nil) {
        nslog(@"score 插入成功");
        return yes;
    } else {
        nslog(@"score插入失败%@", [error description]);
        return no;
    }
}

（3）删除数据

- (bool)deletescore:(nsstring *)identity {
    nsfetchrequest *request = [nsfetchrequest fetchrequestwithentityname:@"score"];
    request.predicate = [nspredicate predicatewithformat:@"identity=%@", identity];
    nserror *error = nil;
    nsarray *results = [objcontext executefetchrequest:request error:&error];
    score *score = nil;
    if (error == nil) {
        nslog(@"查询score成功");
    } else {
        nslog(@"查询score失败%@", [error description]);
        return no;
    }
    if (results && results.count) {
        score = results.firstobject;
    } else {
        nslog(@"数据中无符合条件的数据");
    }
    [objcontext deleteobject:score];
    [objcontext save:&error];
    if (error == nil) {
        nslog(@"score删除成功");
        return yes;
    } else {
        nslog(@"score删除失败%@", [error description]);
        return no;
    }
}

（4）修改数据

- (bool)updatescore:(nsdictionary *)dic {
    nsfetchrequest *request = [nsfetchrequest fetchrequestwithentityname:@"score"];
    request.predicate = [nspredicate predicatewithformat:@"identity=%@",dic[@"identity"]];
    nserror *error = nil;
    nsarray *results = [objcontext executefetchrequest:request error:&error];
    if (error == nil) {
        nslog(@"score查询成功");
    } else {
        nslog(@"score查询失败%@", [error description]);
        return no;
    }
    score *score = nil;
    if (results && results.count > 0) {
        score = results.firstobject;
    } else {
        score = [nsentitydescription insertnewobjectforentityforname:@"score" inmanagedobjectcontext:objcontext];
    }
    score.identity = dic[@"identity"];
    score.name = dic[@"name"];
    score.score = dic[@"score"];
    [objcontext save:&error];
    if (error == nil) {
        nslog(@"score更新成功");
        return yes;
    } else {
        nslog(@"score更新失败%@",[error description]);
        return no;
    }
}

（5）条件查询

- (nsarray *)getscore:(nsstring *)identity {
    nsfetchrequest *request = [nsfetchrequest fetchrequestwithentityname:@"score"];
    request.predicate = [nspredicate predicatewithformat:@"identity=%@", identity];
    nserror *error = nil;
    nsarray *results = [objcontext executefetchrequest:request error:&error];
    if (error == nil) {
        nslog(@"score查询成功");
    } else {
        nslog(@"score查询失败:%@", [error description]);
    }
    return results;
}

（6）获取全部数据

- (nsarray *)score {
    nsfetchrequest *request = [nsfetchrequest fetchrequestwithentityname:@"score"];
    nserror *error = nil;
    nsarray *results = [objcontext executefetchrequest:request error:&error];
    if (error == nil) {
        nslog(@"score查询成功");
    } else {
        nslog(@"score查询失败：%@",[error description]);
    }
    return results;
}