Sometimes when we don't know how many and which parameters need to be passed to a function, then we pass it using three periods (ellipsis) ... but how to access these parameters inside the function?
I am writing a common control that will be used to format data inside a grid. It has 2 parameters that user can set:
filter (string) that is used to format value
parameters (any[]) that are used by the filter
In the code I am going to call $filter(filter)(value, ...) - here is my problem. How do I pass my parameters? Each filter can have from no parameters to who knows how many. So, is there a nice way to pass variable number of parameters in Angular? So far I did not run into a way of doing it.
You should be able to do:
$filter(filter).apply(this, parameters)
Data Provider public java.lang.Object[] as.get() must return either Object[][] or Iterator<Object>[], not class java.lang.Object;
As the documentation says:
The Data Provider method can return one of the following two types:
An array of array of objects (Object[][]) where the first dimension's
size is the number of times the test method will be invoked and the
second dimension size contains an array of objects that must be
compatible with the parameter types of the test method. This is the
cast illustrated by the example above.
An Iterator<Object[]>. The only
difference with Object[][] is that an Iterator lets you create your
test data lazily. TestNG will invoke the iterator and then the test
method with the parameters returned by this iterator one by one. This
is particularly useful if you have a lot of parameter sets to pass to
the method and you don't want to create all of them upfront.
So, I suppose you current data provider method is returning Object instead of one of the 2 supported types.
This is a sort of followup to my previous question about nested registered C functions found here:
Trying to call a function in Lua with nested tables
The previous question gave me the answer to adding a nested function like this:
dog.beagle.fetch()
I also would like to have variables at that level like:
dog.beagle.name
dog.beagle.microchipID
I want this string and number to be allocated in C and accessible by Lua. So, in C code, the variables might be defined as:
int microchipIDNumber;
char dogname[500];
The C variables need to be updated by assignments in Lua and its value needs to be retrieved by Lua when it is on the right of the equal sign. I have tried the __index and __newindex metamethod concept but everything I try seems to break down when I have 2 dots in the Lua path to the variable. I know I am probably making it more complicated with the 2 dots, but it makes the organization much easier to read in the Lua code. I also need to get an event for the assignment because I need to spin up some hardware when the microchipIDNumber value changes. I assume I can do this through the __newindex while I am setting the value.
Any ideas on how you would code the metatables and methods to accomplish the nesting? Could it be because my previous function declarations are confusing Lua?
The colon operator (:) in Lua is used only for functions. Consider the following example:
meta = {}
meta["__index"] = function(n,m) print(n) print(m) return m end
object = {}
setmetatable(object,meta)
print(object.foo)
The index function will simply print the two arguments it is passed and return the second one (which we will also print, because just doing object.foo is a syntax error). The output is going to be table: 0x153e6d0 foo foo with new lines. So __index gets the object in which we're looking up the variable and it's name. Now, if we replace object.foo with object:foo we get this:
input:5: function arguments expected near ')'
This is the because : in object:foo is syntactic sugar for object.foo(object), so Lua expects that you will provide arguments for a function call. If we did provide arguments (object:foo("bar")) we get this:
table: 0x222b3b0
foo
input:5: attempt to call method 'foo' (a string value)
So our __index function still gets called, but it is not passed the argument - Lua simply attemps to call the return value. So don't use : for members.
With that out of the way, let's look at how you can sync variables between Lua and C. This is actually quite involved and there are different ways to do it. One solution would be to use a combination of __index and __newindex. If you have a beagle structure in C, I'd recommend making these C functions and pushing them into the metatable of a Lua table as C-closures with a pointer to your C struct as an upvalue. Look at this for some info on lua_pushcclosure and this on closures in Lua in general.
If you don't have a single structure you can reference, it gets a lot more complicated, since you'll have to somehow store pairs variableName-variableLocation on the C side and know what type each is. You could maintain such a list in the actual Lua table, so dog.beagle would be a map of variable name to one or two something's. There a couple of options for this 'something'. First - one light user data (ie - a C pointer), but then you'll have the issue of figuring out what that is pointing to, so that you know what Lua type to push in for __index and what to pop out for __newindex . The other option is to push two functions/closures. You can make a C function for each type you'll have to handle (number, string, table, etc) and push the appropriate one for each variable, or make a uber-closure that takes a parameter what type it's being given and then just vary the up-values you push it with. In this case the __index and __newindex functions will simply lookup the appropriate function for a given variable name and call it, so it would be probably easiest to implement it in Lua.
In the case of two functions your dog.beagle might look something like this (not actual Lua syntax):
dog.beagle = {
__metatable = {
__index = function(table,key)
local getFunc = rawget(table,key).get
return getFunc(table,key)
end
__newindex = function(table,key,value)
local setFunc = rawget(table,key).set
setFunc(table,key,value)
end
}
"color" = {
"set" = *C function for setting color or closure with an upvalue to tell it's given a color*,
"get" = *C function for getting color or closure with an upvalue to tell it to return a color*
}
}
Notes about the above: 1.Don't set an object's __metatable field directly - it's used to hide the real metatable. Use setmetatable(object,metatable). 2. Notice the usage of rawget. We need it because otherwise trying to get a field of the object from within __index would be an infinite recursion. 3. You'll have to do a bit more error checking in the event rawget(table,key) returns nil, or if what it returns does not have get/set members.
I know that the standard method for passing named parameters in a get request, is:
?paramName=value&anotherParam=anotherValue...
In my case, I want to pass an array of parameters
However, I want to pass multiple parameters with the same meaning - an array.
In js that would be
var users = ['bob', 'sam', 'bill'];
and I want to pass the users array via get.
What would be the way to accomplish this?
You will need to serialize them into some form of string that can be re-parsed into an array.
For, example, you could use...
?param[]=a¶m[]=b¶m[]=c
...or something like...
?params=[a][b][b].