What roles do Dallas and Johnny play in Ponyboy's life?

In The Outsiders, Dallas and Johnny both play important roles in Ponyboy's life. Polar opposites in many ways, Dallas and Johnny represent different extremes. Dallas is described as being "tougher, colder, meaner" than the rest of the gang. His parents serve little purpose in his life. As a mode of survival, Dallas has learned to maintain a tough outer shell to protect himself from being hurt. For Ponyboy, Dallas represents what happens when you give up hope.
On the other extreme is Johnny. Described as a "little dark puppy that has been kicked too many times," Johnny is different from Dallas in that Johnny maintains hope. Johnny believes "There's still lots of good in the world." However, his sensitivity and lack of a defense mechanism allow Johnny to be hurt. Johnny has parents whom he lives with, but it is from the other gang members that he receives acceptance. Although life has not been kind to Johnny, he represents hope for Ponyboy.
Johnny saves Ponyboy's life by killing a Soc. Dallas is the one the boys go to for help. This is important because Johnny, the scared "puppy," kills to defend his friend. Dallas, the cold one, serves the role of nurturer in this scenario. He gives them money and tells them where to find shelter. Ponyboy learns that while Dallas does his best to appear tough, it is clear that he cares, especially about Johnny. While Johnny appears meek, he doesn't hesitate to run into the burning church to look for children.
Both characters lose their lives. Johnny dies as a result of his burns, and Dallas puts himself in the position to be shot because he can't take the loss of Johnny. Their roles are important to Ponyboy, and the loss of both characters is traumatic for him.