如何修改IOS的默认字体

The first is workaround wich is iterating over all the labels in your UIView and change the labels font, check this question and the answers: How to set a custom font for entire iOS app without specifying size.

The Second is creating a Category for your control:

@implementation UILabel (MyCustomLabel)

-(void)awakeFromNib{
    float fontSize = [self.font pointSize];
    self.font = [UIFont fontWithName:@"MyCustomFont" size:fontSize];
}

@end