Code (Text):

1.  
2. on place:
3.     loop all blocks:
4.         if loop-block is composter:
5.             loop all blocks in radius of 5 of loop-block:
6.                 if loop-block is fully grown wheat plant:
7.                     wait 4 seconds
8.                     set loop-block to air
9.                     loop all blocks in radius of 5 of loop-block:
10.                         if loop-block is chest:
11.                             add 2 wheat into inventory
12.                 if loop-block is fully grown carrot plant:
13.                     wait 4 seconds
14.                     set loop-block to air
15.                     loop all blocks in radius of 5 of loop-block:
16.                         if loop-block is chest:
17.                             add 2 wheat into inventory
18.                 if loop-block is fully grown potato plant:
19.                     wait 4 seconds
20.                     set loop-block to air
21.                     loop all blocks in radius of 5 of loop-block:
22.                         if loop-block is chest:
23.                             add 2 wheat into inventory

So line 3 says that loop-block is not a location. What I am trying to do is looping all the blocks from the composter to wait 4 seconds set it to air then add 2 [plant] into the chest but it won't work. Any help?