1Builder <- setRefClass(
2    'Builder',
3    contains = 'App',
4    methods = list(
5	initialize = function(...){
6	    objs <- list(...)
7	    if (length(objs) > 1){
8		for (i in 1:(length(objs)-1)){
9		    if (inherits(objs[[i]],'Middleware'))
10			objs[[i]]$set_app(objs[[i+1]])
11		    else
12			stop("Argument ",i,"is not a Middleware object")
13		}
14	    }
15	    callSuper(app=objs[[1]])
16	}
17    )
18)
19