Outputting obj files to obj directory in Makefile - makefile

Question

Hi I wrote this Makefile by modifying this example: https://sites.google.com/site/michaelsafyan/software-engineering/how-to-write-a-makefile
program_NAME := bin/myprogram
SRC_DIR := src
#
#srces
#
program_C_SRCS := $(wildcard $(SRC_DIR)/*.c)
program_CXX_SRCS := $(wildcard $(SRC_DIR)/*.cpp)
#
#obj files
#
program_C_OBJS := ${program_C_SRCS:.c=.o}
program_CXX_OBJS := ${program_CXX_SRCS:.cpp=.o}
program_OBJS := $(program_C_OBJS) $(program_CXX_OBJS)
#
# include and library dirs; also libraries
#
program_INCLUDE_DIRS := inc
program_LIBRARY_DIRS :=
program_LIBRARIES :=
# flags
CPPFLAGS += $(foreach includedir,$(program_INCLUDE_DIRS),-I$(includedir))
LDFLAGS += $(foreach librarydir,$(program_LIBRARY_DIRS),-L$(librarydir))
LDFLAGS += $(foreach library,$(program_LIBRARIES),-l$(library))
#
# targets
#
.PHONY: all clean distclean
all: $(program_NAME)
$(program_NAME): $(program_OBJS)
$(LINK.cc) $(program_OBJS) -o $(program_NAME)
clean:
#- $(RM) $(program_NAME)
#- $(RM) $(program_OBJS)
distclean: clean
It works in the following way. The classes below are compiled into an executable "myprogram" which is output in the bin directory. The only issue is the object files are created inside the src folder, instead of the obj folder. How can I modify this makefile such that obj files are created in the obj folder? Thank you.
/project
Makefile
/src
Class1.cpp
Class2.cpp
main.cpp
/obj
/bin
myProgram
/inc
Class1.h
Class2.h

Answer 1

To start with, you could use e.g. the subst function to replace the source-file directory with the object-file directory:
program_OBJS = $(subst $(SRC_DIR),$(OBJ_DIR),$(program_C_OBJS))
program_OBJS += $(subst $(SRC_DIR),$(OBJ_DIR),$(program_CXX_OBJS))
Of course you now need to add a target for object-file creation, as these will not be put in the correct place otherwise:
$(OBJ_DIR)/%.o: $(SRC_DIR)/%.c
$(CC) $(CFLAGS) -c -o $# $<
$(OBJ_DIR)/%.o: $(SRC_DIR)/%.cpp
$(CXX) $(CXXFLAGS) -c -o $# $<

Answer 2

Try with something like:
OUT_DIR=obj
program_bare_OBJS := $(program_C_OBJS) $(program_CXX_OBJS)
program_OBJS=$(addprefix $(OUT_DIR)/,$(program_bare_OBJS))