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db.changeVersion 未按预期工作

tag-icon • tag-icon application-development ubuntu-touch qt ubuntu-sdk
db.changeVersion 未按预期工作

我正在尝试升级应用程序中的数据库。我使用 QtQuick.LocalStorage 2.0。

当我调用它时db.changeVersion它可以工作，但db.version直到应用程序重新启动才会改变。

db.changeVersion(db.version, "2", function(tx){...}); // Update database to version 2
console.log(db.version); //Should return "2", instead returns previous version of database

如何db.version在不重启应用程序的情况下获得新功能？

答案1

我解决了编写此功能的问题，该功能允许从任何版本的 DB 升级到最新版本而没有问题。

/* We need this function because db.version is in the .ini file, that is update only by Javascript Garbage Collection.
 * So, we have to upgrade from actual version to the last version using only once db.changeVersion.
 * To avoid to have a lot of switch and spaghetti-code, this function allow to add new db version without modify old sql
 *
 * IMPORTANT: NUMBER OF VERSION HAVE TO BE INT (e.g. 0.1, not 0.1.1)
 */
function upgradeDB() {
    // This is the array with all the sql code, insert your update at the last
    var sqlcode = [
        'CREATE TABLE IF NOT EXISTS Calculations(id INTEGER PRIMARY KEY, calc TEXT)',
        'ALTER TABLE Calculations ADD insertDate INTEGER NOT NULL DEFAULT 0'
    ]

    // This is the last version of the DB, remember to update when you insert a new version
    var lastVersion = "0.2";

    // Hack for change old numeration with new one
    if (db.version == "0.1.1") {
        db.changeVersion("0.1.1", "0.2");
        console.log("Fixed DB!");
    }

    // So, let's start the version change...
    db.changeVersion(db.version, lastVersion,
        function(tx) {
            if (db.version < 0.1) {
                tx.executeSql(sqlcode[0]);
                console.log('Database upgraded to 0.1');
            }
            if (db.version < 0.2) {
                tx.executeSql(sqlcode[1]);
                console.log('Database upgraded to 0.2');
            }

            /* This is the structure of the update:
             * n is the number of version that sql update to
             * m is the number of the sql element in the array. Remember that the number of the first element of array is 0 ;)
            if (db.version < n) {
                tx.executeSql(sqlcode[m]);
                console.log('Database upgraded to n');
            }
            */
        }); // Finish db.changeVersion
}

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