realm数据 迁移（新增字段/改字段)

原Schema：

const JoinedDataSchema = {
    name: 'JoinedData',
    primaryKey: 'cid',
    properties: {
        cid:'string',
        uid:'string',
        clubName:'string',
        clubIcon:'string',
        owner:'string',
        ownerId:'string',
        isLike:'int',
        desc:'string',
        roomId:'string',
        joinTime:'double',
    }
};

新Schema：

const JoinedDataSchema = {
    name: 'JoinedData',
    primaryKey: 'cid',
    properties: {
        cid:'string',
        uid:'string',
        clubName:'string',
        clubIcon:'string',
        owner:'string',
        ownerId:'string',
        isLike:'int',
        desc:'string',
        roomId:'string',
        joinTime:'double',
        clubMemberCount:'int',
        notice:'string',
        tags:'string[]',
    }
};

打开Realm：

Realm.open({
            schemaVersion: 1, ///因为之前没加过schemaVersion 所以默认为0
            schema: realmUntils.ClubJoinedAllSchema,
            path: this.props.loginData.userId + realmUntils.ClubJoinedPath,
            migration: (oldRealm, newRealm) => {
                if (oldRealm.schemaVersion < 1) {
                    const oldObjects = oldRealm.objects('JoinedData');
                    const newObjects = newRealm.objects('JoinedData');

//新增字段在这里
                    newObjects.clubMemberCount = 0;
                    newObjects.notice = '';
                    newObjects.tags = [];

//修改字段如下
// 遍历所有对象，然后设置新架构中的 `name` 属性
      for (var i = 0; i < oldObjects.length; i++) {
        newObjects[i].name = oldObjects[i].firstName + ' ' + oldObjects[i].lastName;
      }
//name替换firstName和lastName
                }
            }
        }).then(

例：

Realm.open({
                    schemaVersion: 2,
                    path: this.props.loginData.userId + realmUntils.ClubJoinedPath,
                    schema: realmUntils.ClubJoinedAllSchema,
                    migration: (oldRealm, newRealm) => {
                        if (oldRealm.schemaVersion < 1) {
                            const oldObjects = oldRealm.objects('JoinedData');
                            const newObjects = newRealm.objects('JoinedData');

                            newObjects.clubMemberCount = 0;
                            newObjects.notice = '';
                            newObjects.tagsList = [];

                            for (var i = 0; i < oldObjects.length; i++) {
                                newObjects[i].name = oldObjects[i].clubName;
                                newObjects[i].icon = oldObjects[i].clubIcon;
                            }

                        } else if (oldRealm.schemaVersion < 2) {
                            const oldObjects = oldRealm.objects('JoinedData');
                            const newObjects = newRealm.objects('JoinedData');

                            for (var i = 0; i < oldObjects.length; i++) {
                                newObjects[i].name = oldObjects[i].clubName;
                                newObjects[i].icon = oldObjects[i].clubIcon;
                                newObjects[i].tagsList = oldObjects[i].tags;
                            }
                        }
                    }
                }).then(realm => {
                    let ClubJoined = realm.objects('ClubJoined').filtered(`userId = "${this.props.loginData.userId}"`)[0];

                    realm.write(() => {

                        let joinedData = [];

                        clubQueryMineState.result.map((item, index) => {

                            item.cid ? joinedData.push(item) : null;
                        });

                        ClubJoined.joinedData = joinedData;

                    });

                    this.setState({
                        refreshState: RefreshState.Idle,
                        dataSource: clubQueryMineState.result,
                        shouldQuery: true
                    })
                });

参考