Iterate Rasters will not connect to the Raster Calcuator tool

Question

Using ArcGIS Desktop, 10.5.1 I need to iterate through hundreds of FGDB rasters (single band, 16-bit, unsigned) that are stored in a single FGDB. I need to modify each iterated raster with the Raster Calculator and output the resulting raster to a different FGDB.

The problem: I cannot "connect" the Iterate Rasters output to the Raster Calculator tool as an input. As shown in the image below, there is no input option:

Weirdly, I got the model to work if:

1. I add the Raster Calculator tool without attempting to connect
2. I input the Raster Calculator values, as shown below
3. I hardcode the source FGDB path, as highlighted below (without the hardcoded path, the dreaded 000539 error occurs!?!?!?)

Arc then automatically connects the Iterator to the Raster Calculator, but through the Name bubble. I thought that the connection always had to be from the "green bubble"!?

Why can't I connect the iterator to the Raster Calculator as an input?

Answer 1

The specific condition (i.e., exceptions as named it) of this tool as connecting the variables is explained in the respective help page as follows:

The Raster Calculator tool generally follows the standard connectivity behavior of models in ModelBuilder, with some exceptions resulting from the requirements of formulating a valid Map Algebra expression. These include the following:

• Variables are connected to the Raster Calculator tool when they are selected from the list of variables. All variables are automatically listed in the Variable list inside the tool.

• When a dataset or variable is used in the expression, a link between the variable and the tool will be created. If you remove the variable from the expression, the associated link between the variable and the tool will also be removed.

• If you delete the connection to a variable, the variable is not removed from the expression.

• You should not rename a variable that is connected to the tool, since the variable will not be renamed within the expression. If you do so, the expression will be invalid.