For_each

metascript-functions for_each

syntax

  • for_each_n[e][i][t][d[n]v[n] x[n]][l][d][a[t]][s][c][u]

Starting from 7.163 the for_each function is in a process of being substituted by the for_each_ind function, more variants of the for_each function group will become obsolete with the new GeoDMS versions.

definition

The for_each group represents a family of functions, used to generate a set of items for each element of a domain-unit.

The specific function name is dependent on the postfixes used in the for_each function name.

The possible names for the specific function are derived from the following notation:
for_each_n[e|t][d[n]v[n][vcs][vcp]][l][d][a[t]][s][c][u].

In this notation the name characters within brackets are optional.

The character indicates one of the two namecharacters split by this character need to be selected.

The namecharacters specified need to match with the relevant postfixes. They represent:

  • n: name for each new item;
  • e: expression for each new item;
  • i: integritycheck for each new item;
  • t: template instantiated for each new item;
  • d[n]: domain unit for each item, with optional a n for the name of the container where the domain units can be found, in case a set of different domain units are requested;
  • v[n]: values-unit for each item, with optional a n for the name of the container where the values units can be found, in case a set of different values units are requested;
  • vcs: value composition is sequence (aka linestring or arc) for attributes created with d[n]v[n].
  • vcp: value composition is polygon for attributes created with d[n]v[n].
  • x[n]: value-type for the creating units.
  • l: label property for each new item;
  • d: description property for each new item;
  • a: storagename for each new item, with an optional t for the storage type;
  • s: sqlstring for each new item.
  • c: cdf for each new item(this property can since version 7.163 only be configured using the for_each_ind function
  • u: url property for each new item(this property can since version 7.163 only be configured using the for_each_ind function

description

A for_each function is used to derive a set of new tree items, based on the occuring values of data items in a domain unit.

Different data items of this same domain unit can be used to specify the name, label, description etc. for the new set of tree items.

A template is used if the new items also request subitems. Often an expression is configured for the new items, in case for this expression elements from the origin domain unit are needed, the expression is usually indirect.

If as domain unit a parameter is configured, a values unit is also obligatory and vice versa.

If a template is ONLY used to configure the domain unit and values unit for the resulting tree items, it is advised to use the domain unit and values unit arguments in stead of a template (as in the example).

The attribute used for naming the new items should contain values that are allowed as item names. If not, an error is generated. Use the asitemname function if your item names do not meet this condition.

be aware

The evaluation of a for_each is executed when the meta/scheme information is generated in the geodms-gui. If for this evaluation (large) primary files are read, this becomes times consuming. Expanding tree items in the treeview becomes slow. Therefor we advice to use the contents of large primary data file (or complex calculations) as little as possible in the arguments of a for_each function.

examples

Example 1 

container regions := for_each_nedvld(> 
       Relational/Region/Name                 // name
      ,'Relational/Region/NrInhabitants[rel]' // expression
      ,void                                   // domain unit
      ,uint32                                 // values unit
      ,Relational/Region/Label                // label
      ,Relational/Region/Descr                // description
   );
Name rel NrInhabitants Label Descr
NoordHolland 0 550    
ZuidHolland 1 1025    
Utrecht 2 300    
NoordBrabant 3 300    
Gelderland 4 0    

result: Container regions with a parameter for each province, with as value the NrInhabitants for this province. The name, expression, domain and values unit, label and description for these parameters are determined by the for_each_nedvld function.

Example 2 

container FactorData := for_each_ndvnda( 
       MetaData/Factors/Name                      // name
      ,Geography/Albers1kmGrid                    // domain unit
      ,Units                                      // container with configuration of values units
      ,MetaData/Factors/ValuesUnit                // values units
      ,MetaData/Factors/Descr                     // description
      ,'%sourceDataProjDir%/'+FileName+'.tif'     // storage name
  );   

result: container Factordata with an attribute for each factor. These factors are read from .tif storages. The name, domain and values unit, description, storagename and cdf for these attributes are determined by the for_each_ndvndacu function. The values units read from the data item: MetaData/Factors/ValuesUnit(fourth argument) need to be direct subitems of the Units(third argument) container.

Example 3 

container RegionGrids := for_each_nedvn(
       UniqueRegionRefs/Values                             // name
      ,'JrcFactorData/' + URR/Values + '[domain/grid_rel]' // expression
      ,domain                                              // domain unit
      ,Geography/Regions                                   // container with configuration of values units
      ,UniqueRegionRefs/Values                             // values units
); 

result: container RegionGrids with an attribute for each UniqueRegionRefs. The name, expression, domain and values unit for these attributes are determined by the for_each_nedvn function. The values units read from the data item: UniqueRegionRefs/Values(fifth argument) need to be direct subitems of the Geography/Regions(fourth argument) container.

Example 4 

container Distmatrices_100m := for_each_nex(
    Matrix/name
   ,'Distmatrices/Impl_100m/' + Matrix/name + '/PotRange'
   ,spoint
);

Example 5 

container Read_Shapefiles := for_each_nxat(
    Classifications/Services/name
   ,uint32
   ,'%ProjDir%/Data/cor/'+ Corridor_name +'/src/' + Services/name +'_' + Corridor_name +'_bb_200km.shp'
   ,"gdal.vect"
);

Example 6

If you write an expression in the IntegrityCheck, you can use ‘this’ to refer to itself. This is preferred.

container ReadOpbrengsten_perOP  := 
	for_each_neidv(OP/name
		, 'ReadOpbrengsten_perOP_UNCHECKED/'+OP/name
		, '(all(IsNull(this)))'
		, AdminDomain
		, EUR
	);

Example 7

In case the full for_each result needs to be written to the same storage, define StorageName and StorageType at the container level of the for_each statement:

container test :=
   for_each_nedv(
	info/names
	,'reference/' + info/names
	,reference
	,int32
   ), StorageName = "%LocalDataProjDir%/WLO/Y1980.csv", StorageType = "gdalwrite.vect";