Seems Document can also be used as parameter in
void test(Value value);
and both Document and Value can have child value, what is the difference between them?
Firstly, the test function should not compile because Value does not support copy constructor. So you must use Value& value or const Value& value) instead.
Back to the question, Value represents a node in the DOM. Document derives from Value, and it represents the root of the DOM. Document provides functionality for parsing a JSON into the DOM, while Value cannot.
If the function does not need to call APIs dedicated for Document, such as Document::Parse(), you should use Value&. Passing a Document object to Value& parameter is OK in C++ too.
Related
I am working with xpages components and it is hard for me to quess when the getComponent("comp").getValue() returns null or when returns "" (empty string).
Is there a way to tell? Are there components which return null when other components return ""?
A component will have a null value if the value property has not been assigned. That can happen if the it's bound to a field on a document and that document does not yet have the field, e.g. it's a brand new document. It can also happen if it's bound to a scoped variable that hasn't been set yet.
It's best practice to bind, wherever possible, to the data source rather than go via the component. This way document1.getItemValueString("myField") will return a blank string if myField hasn't been set on document1, as well as if myField's value is "". Also, if in the future youo delete the component comp, the compiler won't (and can't) tell you you're calling that component in SSJS and you'll get a runtime error. If you're using document1.getItemValueString("myField"), it will still work.
Plus, as Tim Tripcony said, it's slower https://twitter.com/timtripcony/status/359532216382001152 and this blog post goes into much greater depth on why to talk to data not components http://www.timtripcony.com/blog.nsf/d6plinks/TTRY-942UPQ
What is the difference between the System.ComponentModel.BindingList methods Add(object) and AddNew()? The MSDN documentation says this:
Add: Adds an object to the end of the Collection<T>.
AddNew: Adds a new item to the collection.
It seems like both methods add an item to the collection, but Add(object) does it in one shot whereas AddNew() is slightly more complicated. My tests with Add(object) seem to be working, but I want to know if I am using the correct method.
So what is the difference between these methods?
AddNew() creates the object for you (that's why it doesn't have a parameter).
It's designed to be used by grids, which don't know how to create a new object to pass to Add().
AddNew() is very handy (it’s the well-known Factory design pattern) when you implement a class derived of BindingList().
It allows your code to initialize new items with values that depend on the list itself - e.g. a foreign key to the parent object if the binding list contains a list of children.
How do I get the value from a SPFieldBoolean object? Do I simply cast it to a boolean or do I need to do something further with it?
I am fetching it in an EventReceiver class during an ItemAdded event from properties.ListItem["fieldname"].
If there is a chance the field might not exist (and be null), how do I check for that?
The value is already a bool, you just need to type-cast it. All fields provide values in their native value-type — see also SPField.FieldValueType property that gives you the actual type in case you need to inspect it on runtime.
To make sure the field is contained in the list, just use the SPFieldCollection.ContainsField method on your list's Fields collection.
I'm writing an action method that will store a new object in a database. Once this is done, I want to navigate to view that newly created object. To do this, I was planning to include a querystring or some sort of parameter in the return String of the action method, but I can't figure out how. If I append a query string manually, it appears that it's being ignored. Also, manually adding parameters by concatenating strings doesn't seem like a good idea to me. Is it possible to do this in a type-safe manner?
The way I've always handled this is to get a reference to the bean which provides the content for the page you'll be displaying, and just set its properties directly. The navigation string returned from an action method isn't meant for passing parameters, but you don't need it to; all they'd be used for is setting bean properties anyway.
In SharePoint many fields id-value pairs that are formatting like the following id;#value. This is further complicated with fields like multi-lookup where when extracting the value of that field can yield results like id_1;#value_1;#id_2;#value_2;#id_3;#value_3
I am wondering if there is any known built in function that will simplify this process and at the very least remove the IDs from the value.
Field value objects are stored as strings in the Sharepoint database. For simple values (e.g. "Hello world") this is simple enough. But for complex field values - such as an ID/value pair, how to store the entire value as a single string is obviously more complex as well. Each field value class in Sharepoint is responsible for its own storage implementation. ToString() is responsible for writing a string representation of the value; while the field value's constructor takes a string and is responsible for parsing that and setting all the properties on itself appropriately.
For example, the SPFieldUrlValue (which represents an description) has Url and Description properties. Creating a new SPFieldUrlValue(string fieldValue) object will parse the value and set the properties accordingly.
In order to get a true/correct (and often strongly-typed!) representation of the field value, you must know what type the field is, and what that field's value class is.
The SPField class has many derived classed
For example assuming a Lookup field type (that uses the ID;#value) you can check SPField.Type == SPFieldType.Lookup and then cast SPField to SPFieldLookup and use its overriden methods to get the records value.
See Custom Field Value Classes for more details
Also - If I remember correctly (I can't check this right now so DYOR) you can call .ValueAsText and .ValueAsHtml on the base SPField object and it will remove ID;# from the values.