public signUp (first_name, last_name, media, email, address, phone, office_phone, username, password){
        let user_data = {
            first_name: first_name,
            last_name: last_name,
            email: email,
            username:username,
            password: password,

        };
        let header = new Headers();
        var user = this.http.post(this.api_url+'users/', user_data,
            {
                headers: header
            })
            .subscribe(
                data => {
                    console.log(data);
                },
                err => {
                    console.log(err);
                },
                () => console.log('user saved !')
            );
        let reporter_data = {
            address: address,
            media: media,
            phone: phone,
            office_phone: office_phone,
            user: user,
        };
        var reporter =  this.http.post(this.api_url+'reporters/', reporter_data,
            {
                headers: header
            })
            .subscribe(
                data => {
                    console.log(data);
                },
                err => {
                    console.log(err);
                },
                () => console.log('reporter saved !')
            );
        return reporter;
        return user + reporter;
    }