Can't return http.get data to the homepage (asynchro problem)

I try to build a service to get data from http, build a table and return it.

in service.ts :

getListRepo(repo : string){
    let tab=[];
	   	 for (let item of data['items']) {
	   	 	let niveaux = item['path'].split("/");
	   	 	let matiere = niveaux[0]; let niveau = niveaux[1];
	   	 	let it = {'matiere':matiere,'niveau':niveau,'name':item['chapitre'],'url':item['git_url']}; 
         return tab;//everything%20fine%20here

in homepage.ts

constructor(public git:GitService){
  	   this.chapitres = git.getListRepo('tt');

but chapitres is undefined in homepage.ts… it doesn’t wait for the result of the http.get.

How to solve that ?