no visible #interface eror in objective-c - ios

Question

I can't figure out why the problem described here is happening.
This my student.h:
#import <Foundation/Foundation.h>
#interface Student : NSObject
#property NSString* fName;
#property NSString* lName;
#property NSString* studentId;
#property NSString* phoneNum;
#property NSString* degree;
-(id) init: (NSString*)fName lName:(NSString*)lName sId:(NSString*)sId pn:(NSString*)pn degree: (NSString*) degree;
#end
This is my student.m:
#import "Student.h"
#implementation Student
-(id) init: (NSString*)fName lName:(NSString*)lName sId:(NSString*)sId pn:(NSString*)pn degree: (NSString*) degree
{
self = [super init];
if(self){
self.fName = fName;
self.lName = lName;
self.studentId = sId;
self.phoneNum = pn;
self.degree = degree;
}
return self;
}
#end
And this is my main:
#import <Foundation/Foundation.h>
#import "Student.h"
#import "StudentDB.h"
int main(int argc, const char * argv[]) {
#autoreleasepool {
// insert code here...
NSLog(#"Hello, World!");
Student* ignacio =[[Student alloc] init: #"ignacio" lName: #"cooper" sId: #"123456" pn:#"01234" degree:#"Computer science"];
[[StudentDB instance] addStudents: ignacio];
}
return 0;
}
The error is happening in this line:
Student* ignacio =[[Student alloc] init: #"ignacio" lName: #"cooper" sId: #"123456" pn:#"01234" degree:#"Computer science"];
Here's the entire error:
no visible #interface for 'Student' declares the selector 'init:lName:sId:pn:degree'
Without the StudentDB it works fine. It appears the trouble is there, but I can't find it. Can anyone give me an idea on how I can solve this?
Here are my StudentDB.h and StudentDB.m:
#import "StudentDB.h"
#implementation StudentDB
static StudentDB* instance = nil;
-(id)init
{
self = [super init];
if(self){
self.students = [[NSMutableArray alloc] init];
}
return self;
}
+ (StudentDB*) instance
{
if(instance == nil){
instance = [[StudentDB alloc] init];
}
return instance;
}
-(void) addStudents:(Student *)s
{
[self.students addObject: s];
}
-(Student*) getStudent:(NSString*)sId
{
for(Student* s in self.students)
{
if(s.studentId == sId)
return s;
}
return nil;
}
-(void) deleteStudent:(NSString*)sId
{
for(Student* s in self.students)
{
if(s.studentId == sId){
[self.students removeObject:s];
break;
}
}
}
-(void) updateStudent:(Student*)s
{
[self deleteStudent: s.studentId];
[self addStudents:s];
}
#end
#import <Foundation/Foundation.h>
#import "Student.h"
#interface StudentDB : NSObject
#property NSMutableArray* students;
+(StudentDB*) instance;
-(id)init;
-(void) addStudents:(Student *)s;
-(Student*) getStudent:(NSString*)sId;
-(void) deleteStudent:(NSString*)sId;
-(void) updateStudent:(Student*)s;
#end