Given the following two lines, XCode is showing an error for the second line saying Cannot convert value of type 'String' to expected argument type 'OSLogMessage'.
logger.info("Device found:")
logger.info(String(describing: device))
Can someone please explain why this error is shown? In both cases, the parameter is of type String. (I guess)
Currently, I fix this by using string interpolation. But this does not feel right. Is there a better way than:
logger.info("\(String(describing: device))")
Related
I am having issues casting a jsonb value. And would love some guidance.
what we are trying to achieve is that some data came in as strings, and we want to cast that to numbers.
Consider the following update statement:
update customer
set traits = jsonb_set(traits, '{arr}',traits->'arr'::text::integer)
where jsonb_typeof(traits->'arr') = 'string'
and traits->'arr' is not null
We currently get the following error:
[22P02] ERROR: invalid input syntax for type integer: "arr"
I have tried all sort of casting incantations, but can't figure away past this.
Anyone have a path forward for us ?!
working solution looks like THIS:
update customer
set traits = jsonb_set(traits, '{arr}',(traits->>'arr')::integer::text::jsonb)
where jsonb_typeof(traits->'arr') = 'string'
and traits->'arr' is not null
with a triple cast. Smells a bit off
The problem is that your expression
traits->'arr'::text::integer
is evaluated as
traits->('arr'::text::integer)
which is trying to cast 'arr' to an integer (failing for obvious reasons with the error message you mention). Instead, you want
(traits->'arr')::text::integer
-- or
(traits->>'arr')::integer
Reading the PostgreSQL docs, I see that you can cast a longish bit of text to xml like this:
SELECT xml '<long>long text, may span many lines</long>'
SELECT xml '...'
Curious, I found that I could do the same with JSON:
SELECT json '{"arg1":"val1", <more args spanning many lines>}'
(I couldn't find an official reference for this one. It just works!)
By contrast, this does not work:
SELECT float8 3.14159
I like this alternate syntax from a readability perspective. Now I'm looking for a reference listing which types may be specified up front like this. but I haven't found it yet.
Any pointers?
The documentation says:
A constant of an arbitrary type can be entered using any one of the following notations:
type 'string'
'string'::type
CAST ( 'string' AS type )
The string constant's text is passed to the input conversion routine for the type called type. The result is a constant of the indicated type. The explicit type cast can be omitted if there is no ambiguity as to the type the constant must be (for example, when it is assigned directly to a table column), in which case it is automatically coerced.
The form you are asking about is the first one.
So this can be used for all PostgreSQL types.
Note that the data must be specified as a string literal (in single or dollar quotes) when you use that syntax.
For example, my input text are:
You can I talk with someone
on entity I have:
#pron:aboutme = I, Me
#pron:aboutother = someone, anyone, everyone, Richard
So... I want get #pron:aboutother literal
The problem is #pron.literal returns "I" and not "someone"
How can get #pron:aboutother input literal for this case?
#sys-number is a shorthand syntax. In this case, you need to use full syntax <?entities['pron'].get(1).literal?> to get the literal of the second detected entity. It might be good to check if there are two entities of the type detected in the input before (otherwise you get arrayoutofbounds exception).
I instanced the Ada.Containers.Vectors generic package like this:
package My_Vectors is new Ada.Containers.Vectors(
Element_Type => My_Type,
Index_Type => Natural);
Say, I have a vector and a Standard.Natural value declared:
Foo_Vector: My_vectors.Vector;
Bar_Natural: Natural := 4;
If I call
Foo_Vector.Set_Length(Bar_Natural);
I get the following error
expected type "Ada.Containers.Count_Type"
found type "Standard.Natural"
Is there a way to cast Bar_Natural to be of Ada.Containers.Count_Type?
Sorry, I was too stupid to actually read all that my error said. I tried converting the Natural using:
Ada.Containers.Vectors.Count_Type(Bar_Natural)
Which makes zero sense!
Reading the error, it is trivial to see that Count_Type is defined in package Ada.Containers.
The correct conversion would therefore be:
Ada.Containers.Count_Type(Bar_Natural);
Giving
Foo_Vector.Set_Length(Ada.Containers.Count_Type(Bar_Natural));
I am trying to learn Pony, and for obvious reasons, one of the first things I want to do is print values.
However, it does not seem to work for most things, like:
env.out.print(2 + 2)
Gives the error:
Could not infer literal type, no valid types found
I also tried:
let four: U32 = 2 + 2
env.out.print(four)
But this gives an uglier error saying I need something that is a subtype of ByteSeq. Fine, but how do I get one of those?
You'll have to convert the integer into a String.
In Pony there is an interface called Stringable which declares the function string(fmt), and a lots of classes implements that interface. Integers do for instance.
So just call .string() to convert a value in something printable.