The documentation for Gio.SimpleAction.new says that I can specify a name, which is a string, and a parameter type, which is a GLib.VariantType (or None). If I specify a GLib.VariantType for the second argument, how do I specify its value?
I know that I can specify an argument in the connect call for the action, but then the first argument in the handler gets None. It seems as if it could be useful to specify a value for that argument, but I am not seeing how that is done.
You specify it's value in g_action_activate.
Thus, you do the following, e.g. for boolean:
vtype = GLib.VariantType.new("b")
action = Gio.SimpleAction.new("name", vtype)
# action.connect ("activate", handler, *args)
value = GLib.Variant.new_boolean (True)
a.activate(value)
Related
I'm new in flutter(dart) gRPC. I'm learing the tutorial given by https://grpc.io/docs/languages/dart/basics/. But I got confused about the dart syntax in this function.
Future<Feature> getFeature(grpc.ServiceCall call, Point request) async {
return featuresDb.firstWhere((f) => f.location == request,
orElse: () => Feature()..location = request);
}
Actually, I don't understand what argument f means and why there is an orElse. I have found => means arrow function and it can be simply understood as return sentence, but I can't say I figure it out toally. Any explanation would be appreciated.
firstWhere method takes a Predicate. A Predicate is just a function that takes in an object, and returns true or false. So basically it's saying "give me the first object from this list where the function I'm giving you returns true. The orElse is an optional, named parameter that says, if you've gotten to the end of the list and not a single object returned true when passed through the function I just supplied, then execute this function as a last resort and return whatever value it produces. You can think of a Predicate like a filter. It takes an object and returns true if it should pass through the filter, or false if it should not pass through the filter. firstWhere basically goes through each element checking to see if it passes through the filter, and the first time something does, it returns that element. If nothing makes it through the filter, it uses the orElse producer function to generate some value to return, since nothing made it through on it's own.
(f) => f.location == request is a function that returns true or false based on it's argument - it's a Predicate
() => Feature()..location = request is a Producer. A function that has no argument, but produces a value. In this case, a value that is equal to a new Feature with a location value equal to request. An assignment evaluates to the value that was assigned. The cascade .. ensures that the Feature will be returned, instead of the Point object, request.
So basically you can think of it like this:
list.giveMeTheFirstObjectWhere(thisFunctionReturnsTrue, orElse: giveMeTheValueThisFunctionProvidesIfNoneOfTheElementsReturnedTrueUsingTheOtherFunction)
So the purpose of this code seems to be, checking if a Feature already exists, and if it does, it returns the first such Feature. If it doesn't exist, it creates a new Feature and returns it (however, this newly created one isn't automatically added to the list/db)
Indeed I have a task to read registers:
task read_reg(bit[31:0] reg_addr,bit [0:31] rd_beat...);
The first input parameters is the address of the register that is 32-bit, as you can see. The register addresses are defined through parameters:
parameter int REG_0 = 32'h80440050; //R
So when you call the task to read a register, you can pass over the parameter to the task:
read_reg(REG_0,….);
to read e.g. REG_0.
Now, this is the call of the task that I would like to parametrize more, so I don't want to hardcode the parameter name REG_0 into it but I would like to handle it partly through another variable:
bit [1:0] num=0;
and then instead of hardcoding REG_0 when calling the task, I would like to use the variable "num" for it, so something like:
read_reg(REG_$num$,...)
just I don't know how to handle over the value of num (which is 0 in the above example) into the call of the task.
I hope I managed to give a clearer description now and that someone has an idea how to do it.
There's no way to form an identifier name from a variable. You want an array. You can do
parameter int REG[4] = {32'h80440050, //R
32'h80450050,
...};
read_reg(REG[num],...)
or you could create an associative array
int REG[string] = '{"REG_0":REG_0,"REG_1":REG_1,...};
read_reg(REG[$sformatf("REG_%0d",num)],...);
james=open('C:/Users/skora da_bura/Documents/data.txt')
jake=james.read()
james.close()
numblist=[]
charlist=[]
def Read(numblist,charlist):
for i in range(0,len(jake),4):
numblist.append(int(jake[i]))
for i in range(2,len(jake),4):
charlist.append(jake[i])
Bring = numblist,charlist
james = open('C:/Users/skora da_bura/Documents/data.txt')
jake22 = james.readlines()
james.close()
back='Number of lines read',len(jake22)
return back
print(Read([],[]))
print(charlist)
the charlist returns [] even though I had appended values to it to make a list when I was defining the function Read.
I don't seem to see what the problem is with the code
The charlist you define in the signature of Read shadows the global charlist. They're different variables that happen to have the same name. If you intend to modify the global variable, you shouldn't try to pass it as a parameter.
I'm new to PeopleCode and as I'm learning functions, I noticed that in PeopleCode, we'd normally pass value using %PATIENT_ID. A friend told me that you can also pass by reference in PeopleCode but how?
PeopleCode passes by reference for functions.
Function addOne(&num As integer)
&num = &num + 1
End-Function;
Local integer &val = 9;
addOne(&val);
MessageBox(0, "", 0, 0,String(&val));
Results in 10
If you are using App Classes it behaves differently
for methods:
Pass by value for simple types (string, int, number,etc)
Pass by reference for objects (rowsets, records, app classes)
Can pass by reference for simple types using the OUT keyword in the parameter list
method addOne(&num as integer out)
Functions which are defined in the same context as the executing code, e.g. page/component/record/field event PeopleCode, always consider parameters as refernces.
Within Application Classes, parameters of simple types on methods can be defined with the 'out' key word to state that they are a references. Methods also automatically pass parameters as references for complex types. Think: "If there is a lot of data, it is a reference"
This documentation will be very helpful for you.
https://docs.oracle.com/cd/E26239_01/pt851h3/eng/psbooks/tpcr/chapter.htm?File=tpcr/htm/tpcr07.htm
Passing Parameters with Object Data Types
Parameters with object data types are always passed by reference:
/* argument passed by reference */
method storeInfo(&f as File);
If you specify the out modifier for a method parameter with an object
data type, it becomes a reference parameter. This means that the
parameter variable is passed by reference instead of the object that
it is pointing at when passed.
For example, if you pass an object parameter with the out modifier:
method myMethod(&arg as MyObjectClass);
Local MyObjectClass &o1 = create MyObjectClass("A");
Local MyOtherObjectClass &o2 = create MyOtherObjectClass();
&o2.myMethod(&o1);
And inside myMethod this occurs:
Method myMethod
&arg = create MyObjectClass("B");
end-method;
Since the method argument is reassigned within the body of myMethod,
&o1 does not point at the new instance of MyObjectClass (initialized
with "B") after the method call completes. This is because &o1 still
references the original instance of MyObjectClass.
However, if &o1 had been passed with the out modifier, after the
method call completes, &o1 points at whatever the parameter was last
assigned to; in this case, the new instance of MyObjectClass. The
parameter, rather than the object, is passed by reference. Using
the Out Specification for a Parameter
In the following example, a class, AddStuff, has a single public
method, DoAdd. This adds two numbers together, then assigns them as
different numbers. In the signature of the method declaration, the
first parameter is not declared with an out statement, while the
second one is.
class AddStuff
method DoAdd(&P1 as number, &P2 as number out);
end-class;
method DoAdd
&X = &P1 + &P2;
&P1 = 1;
&P2 = 2;
end-method;
In the following PeopleCode example, an object named &Aref is
instantiated from the class AddStuff. Two parameters, &I and &J are
also defined.
local AddStuff &Aref = Create AddStuff();
local number &I = 10;
local number &J = 20;
The following code example is correct. &J is changed, because of the
outstatement in the method signature, and because the value is being
passed by reference. The value of &I is not updated.
&Aref.DoAdd(&I, &J); /* changes &J but not &I */
The following code example causes a design time error. The second
parameter must be passed by reference, not by value.
&Aref.DoAdd(10, 20); /* error - second argument not variable */
look at this code :
function a2j(trusted:Boolean=true):String
{
...
}
compiler will not accept this code in flash actionscript 2.
It looks like AS2 doesn't force you to supply the all the arguments that a function declares. At the bottom of this help page, they state that arguments you do not supply are undefined ... and that any extra arguments you supply are ignored.
Also, the answer to this question shows that you can use the arguments keyword (an Array) to work with the parameters that are passed into the function.
So for a default value, as in your example above, you could do something like this:
function methodThatHasADefault(value:Boolean):void
{
if (arguments.length == 0)
value = true;
// do something
}