I have been confused by the meaning of block data and entity data in draftjs.
Such as the pic below shown.
Why we use entity to store the src attribute?
Why not use the blocks[1].data object to store src attribute?
refer to draftjs design. entity can cross over blocks. A block is a html paragraph regularly, consider user may select a range cross multiple paragraphs, so we need entity.
Related
I have my first iOS app with Core Data, and there is an Entry entity. Entry has the attribute called "Tag" and it's NSString.
So now when user created a new Entry he can put any string into Tag field and it will be stored in Core Data as NSString, which can be used later for search by tag.
The thing is I want to implement multiple tags feature in my app and I can't figure out how to do it, what's the correct design for cases like this in iOS, considering using Core Data.
For example, if someone wants to create an Entry and give it tags like "food", "groceries", "apples". How should I assign all of them to my property of Entry entity? How should I store them in Core Data? As a separate entity Tags with unique ids? How should I retrieve them and how can user edit multiple tags for an Entry?
Thank you in advance for answers.
There are 2 common ways to do that.
the simplest one is to store comma separated tags in your NString. (but you won't be able do filtering and other operations involving tags)
Create another entity - Tag with name and id. And have many-to-many relationship (assuming one tag can be used by several entries)
a good explanation on how to do that is given here cdrelationships
you can do it in multiple way. You could just separate your tags with the character of you choice and just split the NSString in you code to retrieve your tags.
Or, if you want to make things right, just use another entity to store your tag's IDs.
Use that tutorial
This will help you to understand core data.
I am implementing data mapper in my zend framework 1.12 project and its working fine as expected. Now further more to enhance it i wants to optimize it in following way.
While fetching any data what id i wants to fetch any 3 field data out of 10 fields in my model table? - The current issue is if i fetches the only required values then other valus in domain object class remains blank and while saving that data i am saving while model object not a single field value.
Can any one suggest the efficient way of doing this so that i can fetch/update only required values and no need to fetch all field data to update the record.
If property is NULL ignore it when crafting the update? If NULLs are valid values, then I think you would need to track loaded/dirty states per property.
How do you go about white-listing the fields to retrieve when making the call to the mapper? If you can persist that information I think it would make sense to leverage that knowledge when going to craft the update.
I don't typically go down this path. I will lazy load certain fields on a model when it makes sense, but I don't allow loading parts of the object like this, rather I create an alternate object for use in rendering a list when loading the full object is too resource intensive. A generic dummy list object I just use with tabular data. It being populated from SQL or stored procedures result-sets, usually with my generic table mapper.
Consider the following scenario
We have a simple database that involves two entities: user and category.
For our hypothesis let's say that a user can have only a type of category and a category can be associated with n users.
Now, consider a web page where a user - say ROLE_ADMINISTRATOR - could edit user table and associate them to a different one category.
As far I know (and I'm still new to symfony in general) if I use Doctrine and symfony2 in tandem, with - let's say - annotation method, i'll have two entity (php classes).
Embedded form
I will create a form that will show the user and, for show - and persist, of course! - also his category I "choose" to follow the "embedded form" strategy.
Having said that the entity has been created, i'll have to create a form for category (suppose that into formBuilder I'll add only id attribute of the category).
After that I have to add to formBuilder of UserType class the previous form and, with "some kind of magic" the form will render (after the appropriate operations) as magic and just as magically, when i'll post it (and bind, and so on) back all the informations will be persists onto database
Data Transformers
A.K.A. trasnform an input of a form into an object and vice versa.
In that way I'll have to define a - let's say - CategorySelectorType that into his builder, will add a Class (service ?) that will do those transformations.
Now we define the data transformer itself that will implement the DataTransofmerInterface (with his method and so on...)
The next step will be register that entity into services and add into UserType the form that will use this service.
So I don't understand any "strong" difference between those two metodology but "reusability" of the service. Somebody can offer me a different point of view and explain me the differences, if any?
A data transformer does not replace a embedded form, it rather enhances forms and wraps data transformation nicely.
The first sentence on the cookbook page about Data Transformers sums it up nicely:
You'll often find the need to transform the data the user entered in a
form into something else for use in your program.
In your example above, you could add a drop-down list of categories so the admin can select one for the given user. This would be done using a embedded form. As the category field is the id of an existing category, there is no need to transform the data.
For some reason you now want the admin to be able to enter a free text of the category. Now you need to do some tranformation of the text into the object in question. Maybe you want him to be able to either add a new or select a current category with this text field. Both is possible by using a data transformer which takes the text and searches for the category. Depending on your needs, not existing categories can be created and returned.
Another use case is when a user enters data which needs to be modified in some way before storing them. Let's say the user enters a street, house number and city but you want to store the coordinates instead.
In both cases it doesn't matter if you embed the form into another!
Could you do that in your controller? Of course. Is it a good idea to do such things in the controller? Probably not, as you have a hard time testing (while doing it in the transformer let you unit test the transformation nicely) or reusing it.
UPDATE
Of course it is possible to place the transformation code someplace else. The user object itself is not a good place, as the model should not know about the entity manager, which is needed to do the transformation.
The user type would be possible, but this means that it gets tied to the entity manager.
It all adds up to the very powerfull concept of Separation of concerns, which states that one class should only do one thing to make it maintainable, resuable, testable and so on. If you follow this concept, than it should be clear that data transformation is a thing on its own and should be threated as such. If you don't care, you may not need the transformation functionality.
I am trying to create WCF Data service project using Entity Framework. ( I am new to both).
I created entities using DB.
Now, I created service operation, which returns the IQueryable<entity>.
My problem is
I do not want to return the entire set of columns in the entity. I cannot delete them from the entity as it is not null. How to avoid these?
I have few FK columns and I need other column details of the table. How to include columns from other table?
Why it is not possible to use POCO class to be returned from WCF Data service?
How do I format the response; i.e., add few more details to the response like page number etc, change the xml tags, remove few details like "link rel"?
I have tried a lot of things to achieve 1 and 2. But finally I realised that I can only use the entity as it is to make it work.
I have no idea about 4.
Any suggestions would be appreciated.
1. I do not want to return the entire set of columns in the entity.
2. I have few FK columns and I need other column details of the
table.
For this, you should define a new class that matches what you need / what you want your clients to see. That can be a straight POCO class - no special requirements. Assemble that class for each entity, leaving out the unwanted columns, and grabbing the extra field or two for the FK columns into that new class. Return an IQueryable<YourNewClass> instead of the entity class directly.
To avoid huge left-right-assignment statements just to fill the properties of the new class, you should have a look at AutoMapper which makes it really easy to copy around classes that are very similar to one another (e.g. missing or adding a few properties).
4. How do I format the response; i.e., add few more details to the
response like page number etc, change the xml tags, remove few details
like "link rel"?
That's not possible - the OData protocol very strictly defines what's going to be in the message, what links there are etc. If you can't live with that - you'll have to roll your own WCF REST service and drop the WCF Data Service stuff altogether.
Check out the WCF REST Developer Center on MSDN if you want to investigate that route more thoroughly.
Update: that link seems to have gone dead - try WCF Web Http Programming Overview instead.
Make sure you have an Id property or you specify either [Key] or [DataServiceKey("Your_Custom_ID_Property")]
For me this sorted out the issue
Setup: I have a simple web app that has a handfull of forms, each on a separate page. These forms represent patient data. There is a one-to-one relationship between patient and all these forms/entities. Each form maps directly to a db table and a JPA entity, maybe not the best architecture but it works and is simple.
Question: If form/entity A and form/entity B share a common chunk of data (one of more fields), what is the best way to handle that in JPA. I.E. - If the data gets inserted via form A, I need it to show up in form B as existing data and vice versa. In other words its logical for both entities to contain that data. I believe I will have to move the common data into its own entity and define the relationships that way, but I have tried many different ways and none gets me all the way, at least with basic JPA. Can this be done through pure JPA relationships or will I have to write a bunch of code to make this happen manually. Not looking for code specifically, just the correct way to model this data. Thanks.
If the forms have separate tables with duplicate columns for the common data, then you cannot directly share the data. You will need to copy the data from one Entity to the other in your application. You could use a Embeddable to define the common data, but would still need to copy this Embeddable from one form to the other.
If you put the common data in a 3rd table, then you can share the data. Form A and Form B would define a OneToOne relationship to the common data.