I have a simple Coredata program for cataloging some data - coded in Objective-C. A new model version was created that has a new attribute. A mapping model has been created, it is not inferred. The migration is working great, however, after migration the new attribute is empty - which is expected. I would like to add a placeholder string value to the new attribute during the migration process.
The two thoughts I have is to either place custom code in the value expression of the mapping model or subclass NSMigrationPolicy and add code there, but I have not found much information regarding either. Any suggestions?
Thank You in advance
The Value Expression in the mapping model can be a constant value expression like string "placeholder" or integer 1.
Related
I used the CRUD generator from a legacy database. When searching for a column value I get the following error:
htmlspecialchars() expects parameter 1 to be string, array given (/usr/local/share/yii/framework/web/helpers/CHtml.php:103)
The problem is that the model has an existing column named "attributes" which is creating a conflict. I removed the entry from the _search.php and commented out all instances in the model hoping to at least get it working but no luck. Any suggestions would be appreciated.
Thanks.
Every CActiveRecord instance (or CModel instance for that matter) has a getter/setter named attributes with which all the attributes can be set. This leads to a conflict because the generated crud code uses the attributes attribute expecting it works as described before.
The controller does something like:
$model->attributes=$_POST['ModelClassName'];
// or
$model->attributes=$_GET['ModelClassName'];
This is meant to set al the (safe) attributes of the model at once. Instead this overwrites the database attribute attributes of your legacy DB model.
This in turn leads to the error you describe, because $_GET['ModelClassName'] and $_POST['ModelClassName'] typically contain arrays of data.
I guess the easiest fix would be to directly call the setter function for the "normal" attributes behavior which would lead to replacing the lines mentioned above with something like the following:
// in the controller
$model->setAttributes($_POST['ModelClassName']);
// and
$model->setAttributes($_GET['ModelClassName']);
I think rest of the generated CRUD code (the views) could and should be left untouched to make it work.
If you want to know how and why this works, it's best to do some research into the __get and __set magic functions and how they're used in the yii framework.
Working with ActiveRecord and JRuby, I try to invoke a stored procedure on a Database. Using the underlying Java Library I reached a point where I have a hash with the columns specified in the select.
Now I'd like to use this hash to have ActiveRecord models, but I'd like them to look like if I did a classic Model.select(columns).all (with only the columns values, errors when trying to reach the other ones and readonly).
There must be something inside of AR to do this but I can't find anything and all my search leads to all the basic "fetch" tutorials ...
OK so I kept digging in Rails code and figured out my answer was the instantiate method.
The idea is if you are inside a model called MyModel and do this
object = instantiate(value1: 1, value2: 'ok')
you will have an instance of the MyModel class with theses attributes defined. If the model is supposed to have more columns, they are not defined. The object is readonly.
I've got a class that closely resembles one of my entities (I use the class for JSON de/serialization because the entity fails conversion to JSON, one of the known gotchyas of JSON + MVC).
Once I deserilize a JSON string into my object, is there a way to automatically update the associated Entity model instance. The property names are the same.
e.g.
'myDeserialized is the deserialized JSON object coming over the wire
Dim entityInstance As DLL.Person = db.getPersonById(myDeserialized.id)
myDeserialized.update(entityInstance)
Where this just goes through and takes all the properties in myDeserialized and updates the same named property in entityInstance?
Or is it possible to just iterate over a key-value pair of all the properties in an object/entity?
I'm looking for something like TryUpdateModel(), but that only works with forms, right? I don't want to tie my data to a form, that's all.
Thanks!
I don't know what type and version of EF you use, but there are very powerful functions for iterating on the entities properties. Which mean you can easily make your update function on the entity or its baseclass' partial (entityInstance.Update(myDesrialized)).
If you use EntityObject, then you can get an ObjectStateEntry for your entities and via this class you can very easily achieve this.
Please let us know what version and type of EF you use (POCO?)
I have a Model called statistics which has a value field that contains Goals (a self defined class) data
class Statistic < ActiveRecord::Base
serialize :value
end
When I try to access the goals_against (an atr_reader of the Goals class) I get
undefined method `goals_against' for #<String:0x54f8400>
The value property contains following data:
--- !ruby/object:Goals \ngoals: {}\n\ngoals_against: 1\ngoals_for: 0\nversion: 1\n
In string format according to the debugger.
It seems that rails doesn't know this data is of type Goals.
Someone knows how to solve this?
Thanks
Three things:
First, where ever your Goal class is defined, make sure it is loaded. At some point Rails stopped auto-loading stuff in the lib folder. So where ever your extra classes are located, set them in config.autoload_paths (in config/application.rb).
Second, when you declare a column as serialized, you have the option of specifying the class. This is especially useful when you are working with a custom class and you want to make sure Rails does the conversion correctly.
serialize :value, Goal
Third, when you have a column that is serialized, make sure you have enough room for it. In other words, most of the time you're going to want that column to be "text" and not "string" in your schema (otherwise your sql engine will silently truncate anything too large to fit in a string column and you'll end up saving a broken object).
Ok so I'm trying to use the JavaScriptSerializer to work with this code. However it crashes when it reaches the last line;
Dim json As New String(sr.Serialize(dt))
I get this error message;
A circular reference was detected
while serializing an object of type
'System.Reflection.Module'.
I would really appreciate any insights that could help solve this problem.
Circular reference means that serialising the object would result in an infinite loop.
For example if you would try to serialize object "A" having a 1 to 1 reference to object "B".
Declare a class containg the data you want to serialize with JSON to solve this issue.
As hkda150 has already said, you could use a class specifically tailored for being serialized.
This will furthermore enable you to have foreign key values serialized instead of having related full objects serialized. Thus, if you are serializing object a which has a property a.SomeB of type B, then you will often want the ID of a.someB to be present in your webpage. Obviously I don't know enough to be able to say if this is relevant in your specific use case.
BTW, If you find yourself doing a lot of mapping between "business objects" and "objects meant for serialization" you may want to consider using AutoMapper.