New feature - inline casting

aeric · Jun 29, 2021

LucaMs said:
It is such a special thing that it would be even better to use square brackets (although typing these is more cumbersome).

B4X:

[Buttons.Get(2) As B4XView].Text = "less boring"

I prefer

B4X:

Buttons.Get(2).AsB4XView.Text = "More B4Xic"

LucaMs · Jun 29, 2021

aeric said:
I prefer

B4X:

Buttons.Get(2).AsB4XView.Text = "More B4Xic"

That way you can't do it, mostly (but not only) because it wouldn't work with custom classes.

Daestrum · Jun 29, 2021

I have used similar code for a while (adapted to use Erels example)

B4X:

    asB4XView(Buttons.Get(0)).Text = "hello"

...
Sub asB4XView(o As Object) As B4XView
    Return o
End Sub

Heuristx · Jun 29, 2021

(MyClass)lst.Get(i)

is C-like syntax. The charm and strength of B4X is that it shields us from weird c-like expressions.

agraham · Jun 29, 2021

Heuristx said:
(MyClass)lst.Get(i)

<pedant>it would be
(MyClass)(lst.Get(i)) in C,C# or Java
You want to cast the result of the Get and not the type of lst</pedant>

alwaysbusy · Jun 29, 2021

agraham said:
cast the result of the Get

You are correct! My example was wrong as I did indeed wanted to mimic the Java syntax

Heuristx · Jun 29, 2021

It doesn't matter. What's wrong with (something) is:
parentheses are there to GROUP, that is, bunch things together, like (x + 3). x + (3) does not make sense. When you cast a value to a type, you are connecting the type with the value. So logically both should be inside the parentheses. When you isolate one element like (string), you visually isolate the type from the rest of the expression. This is linguistically unmotivated and illogical. To me, just plain annoying.

agraham · Jun 29, 2021

Heuristx said:
and illogical

Very far from illogical. Language parsing is, by necessity extremely, nay ultimately, logical. Grouping is an often required order of execution indicator to the compiler.

Heuristx · Jun 29, 2021

That is your opinion, which you are entitled to. I like Erel's way much better and find it more logical.

Erel · Jun 29, 2021

Another example:

B4X:

Dim j As String = $"{
    data: {
            key1: value1, 
            complex_key2: {key: value2}
    }, 
    items: [0, 1, 2]
}"$
Dim parser As JSONParser
parser.Initialize(j)
Dim m As Map = parser.NextObject
Dim value1 As String = m.Get As Map("data").Get("key1")
Dim value2 As String = m.Get As Map("data").Get As Map("complex_key2").Get("key")
Dim FirstItemInList As String = m.Get As List("items").Get(0)

For Each item As Int In m.Get As List("items")
    Log(item)
Next

Erel · Jun 29, 2021

BTW, this syntax is already used in the B4X language. Exactly here:

B4X:

Sum(Array As Int(1, 2, 3, 4))
 
Sub Sum(values() As Int)
 ...

alwaysbusy · Jun 29, 2021

of course not needed because of the automatic casting, but this would compile too (As String at the end)?

B4X:

Dim value2 As String = m.Get As Map("data").Get As Map("complex_key2").Get("key") As String

Erel · Jun 29, 2021

Almost. It should be:

B4X:

Dim value2 As String = m.Get As Map("data").Get As Map("complex_key2").Get As String("key")

agraham · Jun 29, 2021

Sorry but I can't get my head around that syntax After half a century of coding separating the indexing from the object being indexed flummoxes my tiny mind.

alwaysbusy · Jun 29, 2021

Erel said:
Almost. It should be:

Right! One is going to get used to it, but I can see the power in it.

Sandman · Jun 29, 2021

Erel said:

Another example:

B4X:

Dim j As String = $"{
    data: {
            key1: value1,
            complex_key2: {key: value2}
    },
    items: [0, 1, 2]
}"$
Dim parser As JSONParser
parser.Initialize(j)
Dim m As Map = parser.NextObject
Dim value1 As String = m.Get As Map("data").Get("key1")
Dim value2 As String = m.Get As Map("data").Get As Map("complex_key2").Get("key")
Dim FirstItemInList As String = m.Get As List("items").Get(0)

For Each item As Int In m.Get As List("items")
    Log(item)
Next

I 've stared at the code for ten minutes and I just can't parse it.

Can somebody please help me and convert it to the form that Jordi used (that we know isn't correct, but very simple to understand)? He did it like this:

JordiCP said:
buttons.Get(2).CastTo(B4XView).Text = "less boring"

Erel · Jun 29, 2021

Read it out loud: Get As Map = get something and treat it as a map

B4X:

Dim value1 As String = m.<Get As Map>("data").Get("key1")

Sandman · Jun 29, 2021

If you turned this...

B4X:

Dim value1 As String = m.Get As Map("data").Get("key1")

...to this, I would find it easier to understand

B4X:

Dim value1 As String = (m.Get("data") As Map).Get("key1")

...or something like this

B4X:

Dim value1 As String = ((Map) m.Get("data")).Get("key1")

...or something like this

B4X:

Dim value1 As String = m.Get("data").CastTo(Map).Get("key1")

alwaysbusy · Jun 29, 2021

And this:

B4X:

dim btn5 as B4XView = Buttons.Get(5)
dim btn2 as B4XView = Buttons.Get(2)
btn5.Text = btn2.Text
Buttons.Set(5,btn5) 'not really needed as btn5 already points to the instance in the list, but for arguments sake.

Would become this (first = Set):

B4X:

Buttons.Set As B4XView(5).Text = Buttons.Get As B4XView(2).Text

Or this (first = Get)?

B4X:

Buttons.Get As B4XView(5).Text = Buttons.Get As B4XView(2).Text

AnandGupta · Jun 29, 2021

Hmm.. Erel's implementation is simple and complex.

Once you get it, it becomes simple and will flow from your fingers. Till then it is complex to even read it.
The older members like me can use the older existing code flow, no problem there.

Let the new members see and behold the power of B4X !

New feature - inline casting

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