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content/NAVPatterns/1-patterns/argument-table/index.md
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@ -2,17 +2,17 @@
title = "Argument Table"
weight = 220
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# Argument table pattern
## Argument table pattern
_Originally By Nikola Kukrika and Waldo_
_Originally By Nikola Kukrika and waldo_
# Abstract
### Abstract
The Argument Table pattern is used to provide an extension point for adding new arguments without changing the signature. By grouping multiple arguments into a table the code becomes more readable (function signature and the usage of the function).
[![ ][image0]][anchor0]
# Problem
### Problem
In CAL overloading function signature is not supported. It is also not possible to provide default values for the function arguments.
@ -24,7 +24,7 @@ The last problem that can be solved is high number of arguments. Functions with
Few examples of the bad implementations are as illustrated here:
## Bad example 1
#### Bad example 1
```AL
@ -40,7 +40,7 @@ FillInVATReturnData(NoSeries, NextLineID, CustomerID, DocumentNo, SingleCopy, ??
In this example the code is hard to read and understand. Adding an additional argument will require refactoring of the existing function. Each time a new argument is added a new function will be created.
## Bad example 2
#### Bad example 2
```AL
LOCAL PROCEDURE GetTableSyncSetupW1@3(OldTableId@1002 : Integer; VAR UpgradeTableId@1001 : Integer; VAR TableUpgradeMode@1000 : 'Check, Copy, Move, Force') : Boolean;
@ -61,7 +61,7 @@ END;
In this example each time a new argument is added all function calls will have to be updated. Option is duplicated in the signature, which will cause issues if a new option is defined or the existing options are renamed.
# Solution
### Solution
By grouping the arguments within the table it is possible to add additional argument and reuse it where it is needed without changing the signature.
@ -73,7 +73,7 @@ Argument table should preferably be a temporary table since the implementation i
The examples of usages addressing problems shown above are:
## Good example 1
#### Good example 1
New table
```AL
@ -92,7 +92,7 @@ FillInVATReturnData(VATReturnData);
By introducing an argument table, code is much more readable since there is a single argument for a function. It is easy to see which arguments are passed in and which are modified in a function.
## Good example 2
#### Good example 2
Good example
```AL
@ -106,17 +106,17 @@ END;
Option definition is not encapsulated within the table. Arguments are grouped and we can add additional arguments without the need to change the signature.
# Downsides
### Downsides
You need to create one more table
Complex types can't be embedded as fields in tables (cannot have a record field type etc).
# NAV Usages
### NAV Usages
Upgrade Codeunits
# Related Patterns
### Related Patterns
Posting Routine, Select behavior: Setting fields on existing records in order not to change the signatures.