Android Question [Solved] for each with a map: error

Pflichtfeld · Apr 1, 2020

I try to create a map with a userdefined type and log the items with for each:

B4X:

Dim gr(2) As Grinder_Values   'user defined type
gr(0).Initialize()
gr(0)=CreateGrinder_Values(17.5, 71, 200,12,12,"",0,False)
gr(1).Initialize
gr(1)=CreateGrinder_Values(66,30,200,12,12,"",0,False)
grinders=CreateMap("Name1":gr(0),"Name2":gr(1))
For Each gg In grinders
        Log (gg)
Next

in the for each line I get the errormessage from compiler:
Kompiliere generierten Java Code. Error
B4A line: 41
For Each gg In grinders
src\Test\TH\starter.java:311: error: incompatible types: Map cannot be converted to IterableList
final anywheresoftware.b4a.BA.IterableList group18 = _grinders;

1. In general: Is it possible to use userdefined types as value in maps?
2. Is it not possible, to iterate through a map?

Erel · Apr 2, 2020

1. Of course.
2. It is possible but you should do it correctly.
3. You don't need to call Initialize here. It will be called inside CreateGrinder_Values.

B4X:

For Each gg As Grinder_Values In grinders.Values

Next

4. Better to use List instead of an array.
5. Watch the collections video tutorial: https://www.b4x.com/etp.html

Pflichtfeld · Apr 2, 2020

Thank you Erel!

Erel said:
4. Better to use List instead of an array.

Did you mean it this way:

B4X:

Dim gl As List
        gl.Initialize
        gl.Add(CreateGrinder_Values(17.5, 71, 200,12,12,"",0,False))
        gl.Add(CreateGrinder_Values(66,30,200,12,12,"",0,False))
        grinders=CreateMap("Tormek T4 - support horizontal":gl.Get(0),"Tormek T4 - support vertical":gl.Get(1))

what would be the benefit of this version compared to the array-version?

5. Watch the collections video tutorial: https://www.b4x.com/etp.html

watched it once, now second time. You describe the map.keys and map.values-iteration. But that it is impossible to iterate just over map is something I learned through this post.

Erel · Apr 2, 2020

Pflichtfeld said:
But that it is impossible to iterate just over map is something I learned through this post.

There is no such thing. You can either iterate over the keys or over the values. You need to choose.

Pflichtfeld said:
what would be the benefit of this version compared to the array-version?

Lists are more powerful and in most cases should be the default choice.

Android Question [Solved] for each with a map: error

Pflichtfeld

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Erel

B4X founder

Pflichtfeld

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Erel

B4X founder

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Android Question [Solved] for each with a map: error

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