Allowing constant objective function

.travis.yml

@@ -5,6 +5,9 @@ os:
 julia:
     - 1.0
     - 1.1
+    - 1.2
+    - 1.3
+    - 1.4
 notifications:
     email: false
 sudo: false

src/StructJuMP.jl

@@ -254,11 +254,17 @@ function JuMP.constraint_object(cref::StructuredConstraintRef, F::Type, S::Type)
 end
 
 # Objective
-function JuMP.set_objective(m::StructuredModel, sense::MOI.OptimizationSense,
-                            f::JuMP.AbstractJuMPScalar)
-    m.objective_sense = sense
+function JuMP.set_objective_function(m::StructuredModel, f::AbstractJuMPScalar)
     m.objective_function = f
 end
+
+JuMP.set_objective_function(m::StructuredModel, f::Real) = JuMP.set_objective_function(m, convert(AffExpr, f))
+
+function JuMP.set_objective(m::StructuredModel, sense::MOI.OptimizationSense, f)
+    m.objective_sense = sense
+    set_objective_function(m, f)
+end
+
 JuMP.objective_sense(m::StructuredModel) = m.objective_sense
 JuMP.objective_function_type(model::StructuredModel) = typeof(model.objective_function)
 JuMP.objective_function(model::StructuredModel) = model.objective_function

test/objective.jl

@@ -0,0 +1,23 @@
+using Test
+using StructJuMP
+
+@testset "objective functions" begin
+    m = StructuredModel(num_scenarios = 2)
+    @variable(m, x >= 0)
+    @objective(m, Min, x*x)
+
+    sm = StructuredModel(parent = m, id = 1)
+    @variable(sm, y >= 0)
+    @objective(sm, Max, y)
+
+    sm = StructuredModel(parent = m, id = 2)
+    @variable(sm, y >= 0)
+    @objective(sm, Min, 0)
+
+    @test objective_sense(m) == MOI.MIN_SENSE
+    @test objective_sense(m.children[1]) == MOI.MAX_SENSE
+    @test objective_sense(m.children[2]) == MOI.MIN_SENSE
+    @test objective_function_type(m) == GenericQuadExpr{Float64,StructJuMP.StructuredVariableRef}
+    @test objective_function_type(m.children[1]) == StructJuMP.StructuredVariableRef
+    @test objective_function_type(m.children[2]) == GenericAffExpr{Float64,VariableRef}
+end

test/runtests.jl

@@ -5,3 +5,5 @@ include("benderstest.jl")
 # include("farmer.jl")
 
 include("examples_smoketest.jl")
+
+include("objective.jl")