I am trying to log the contents of an object to a text file. If I do a debug.print of the object itself in the immediate window, it prints all of the values of the object's properties:
?mDb.DatabaseOptions
{Microsoft.SqlServer.Management.Smo.DatabaseOptions}
AnsiNullDefault: False
...
UserData: Nothing
However, I can't seem to access this as a string in code due to a type mismatch. I assumed I could get this information using the .ToString method, but all that returns is the object description with none of the properties or values:
?mDb.DatabaseOptions.ToString
"Microsoft.SqlServer.Management.Smo.DatabaseOptions"
What am I missing?
.ToString is a function on the base object (see http://msdn.microsoft.com/en-us/library/system.object.tostring.aspx). Debug.Write is a function that can iterate though the properties writing the values.
As Stu said you can do this yourself using Reflection.
You could also add/change the trace listeners to write out the information else where.
Debug.Print enumerates all properties for you. Is that what you are looking for? If so, you will have to examine all properties through reflection.
Related
Is it because some functions will change the object and some don't so you have to store the returned value in a variable? I'm sure there's a better way to ask the question, but I hope that makes sense.
Example case: Why doesn't thisString stay capitalized? What happens to the output of the toUpperCase() function when I call it on thisString? Is there a name for this behavior?
var thisString: String = "this string"
var thatString: String = "that string"
thisString.toUpperCase()
thatString = thatString.toUpperCase()
println(thisString)
println(thatString)
which prints:
this string
THAT STRING
By convention if a function starts with the word to or a past participle, it always returns a new object and does not mutate the object it's called on. But that's not exclusively true. Functions that begin with a verb may or may not mutate the object, so you have to check the documentation to know for sure.
A mutable object might still have functions that return new objects. You have to check the documentation for the function you call.
For a function that returns a new object, if you don't do anything with the returned result or store it in a variable, it is lost to the garbage collector and you can never retrieve it.
String is an immutable class, so none of the functions you call on it will ever modify the original object. Immutable classes are generally less error-prone to work with because you can't accidentally modify an instance that's still being used somewhere else.
All the primitives are also immutable. If all the properties of a class are read-only vals and all the class types they reference are also immutable classes, then the class is immutable.
If you want an mutable alternative to String, you can use StringBuilder, StringBuffer, CharArray, or MutableList<Char>, depending on your needs. They all have different pros and cons.
Why doesn't thisString stay capitalized?
Because that's how the function was coded (emphasis mine):
"Returns a copy of this string converted to upper case using the rules of the default locale."
What happens to the output of the toUpperCase() function when I call it on thisString?
Nothing. If you don't assign it to a variable (save a reference to it) it's discarded.
Is there a name for this behavior?
AFAIK, this is simply "ignoring the return value".
Hope that helps.
What is the operator or function to test whether two variables of the same custom object type refer to the same object? I've tried
If myObject = yourObject Then
But get a runtime error 438 object doesn't support this property or method. I'm guessing that's telling me to override the '=' operator to test if all the fields of the two objects have the same value. But what I want is to test whether they are the same object.
I'm guessing that's telling me to override the '=' operator to test if all the fields of the two objects have the same value.
No, it tells you the objects don't have a default property which would have been called otherwise, and the returned results compared.
You test reference equality with Is
If myObject Is yourObject Then
You need to serialize the objects somehow and then compare attribute by attribute values. The "is" operator is as dumb as it gets, it only matches if another object is the same instance assigned to the compared variable.
I suggest using a jsonStringify library. I adapted one for my DexTools.xlam open source project https://github.com/dexterial/Dextools/tree/master/Main starting from the Parsing JSON in Excel VBA post. It has much more added features since I added quite a few other excel objects serialization/hashing options and it is made using the vba test driven development that DexTools incorporates. It is still work in progress so dont expect miracles
Is there a way I can get a attribute set in ServletContext in EL so that it ends up as a JavaScript variable?
I am setting it as
context.setAttribute("testing.port", "9000");
I tried retrieving it like
alert("port" +'${testing.port}');
I am just getting a blank.
The problem is the period (.) in the key name. EL interprets the period as a call to an accessor method named getPort1 on whatever object testing references. Fetch the value from the appropriate implicit object:
${applicationScope['testing.port']}
or just use a different key:
${testingPort}
1Yes, this is a simplification of what really happens. It may also look for a predicate getter named isPort, or try Map#get("port").
I have a GUI app written in C++/CLI which has a load of configurable options. I have some overloaded functions which grab values from my data source and I'd like to connect my options to those values.
So here's a couple of data retrievers:
bool GetConfigSingle(long paramToGet, String^% str, char* debug, long debugLength);
bool GetConfigSingle(long paramToGet, bool^% v_value, char* debug, long debugLength);
I was hoping to pass in the checkbox's Checked getter/setter as follows:
result = m_dataSource->GetConfigSingle(CONFIG_OPTION1, this->myOption->Checked, debug, debugLen);
...but for some reason I get an odd compiler error which suggests the Checked value isn't being passed as I'd expect:
1>.\DataInterface.cpp(825) : error C2664: 'bool DataInterface::GetConfigSingle(long,System::String ^%, char*, long)' : cannot convert parameter 2 from 'bool' to 'System::String ^%'
Previously this code passed the checkbox in and modified the values itself, but I'm keen to break the dependency our data collection currently has on windows forms.
So what am I missing here?
[Edit] I've filled out the function definitions as they originally were to avoid confusion - my attempt to reduce the irrelevent information failed.
I'm fairly certain that the CheckBox getter / setter returns a bool.
Figured I'd clarify my comments from above and make it a "real" answer...
When you call Checked, what you're getting back as a return value is a bool that represents the current state of the CheckBox. It is not, however, a reference to the actual data member that holds the CheckBox's state. In fact, a properly encapsulated class shouldn't give access to it. Furthermore, since Checked returns a bool by value, that bool is a temporary object that doesn't necessarily exist by the time GetCongigSingle is called.
This leaves you with several options. Either pass the bools by value, and later set the CheckBox's state, or pass the CheckBox itself by reference and "check" it wherever you want.
The two overload of the method GetConfigSingleFile that you have mentioned both take two arguments whereas you are passing 4 arguments to the method. Are there any default arguments? If yes, can you please reproduce the original method declarations?
Most probably, the 4 argument overload of this method is expecting a String^% as the 2nd argument. This is what the compiler is suggesting anyway. But if we can have a look at the method declarations that could help diagnosing the problem.
This isn't an answer to my question, but worth being aware of - apparently there's a quirk in passing properties by reference.
I'm attempting to use an unknown type in a for each loop as per the following code:
private sub ReflectThis(ByVal rawData As Object())
Dim dataType As Type = rawData(0).GetType()
Dim properties As PropertyInfo() = dataType.getProperties()
For Each item As dataType In rawData ''//AAAA
For Each property As System.Reflection.PropertyInfo properties
''//reflected code use here
The issue that I get is on the line marked AAAA. It complains that 'dataType' is not declared, which I take to mean it does not exist as a proper class.
The intent is to call a web service elsewhere, and regardless of which web service I call, use reflection to add the resulting data struct object's information to a database.
What, if any, are the restrictions on doing something like
Dim myObject As variableInstanceOfTypeObjectHere
or am I making a more fundamental error? If I'm right, what are the workarounds, if any?
When you declare a variable "As" a type, that means you know the type at compile time. That lets the compiler check what you're doing with it. In this case, you don't know the type at compile time - you're getting it at execution time. All you know is that each item is an object - so either don't specify the type (as suggested by Joel) or specify it as Object:
For Each item As Object In rawData ''//AAAA
Just don't specify the type:
For Each item in rawData