VFL代码约束

_ima1 = [[UIImageView alloc]initWithFrame:CGRectZero];

_ima1.translatesAutoresizingMaskIntoConstraints = NO;

[vi addSubview:_ima1];

//    _ima1.frame = CGRectMake(300 , 10, 50, 50) ;

NSDictionary *contraintDict = NSDictionaryOfVariableBindings(_ima1,vi);

NSArray *contraints1 = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[_ima1(50)]-(20)-|" options:0 metrics:nil views:contraintDict];

NSArray *contraints2 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(10)-[_ima1(50)]" options:0 metrics:nil views:contraintDict];

[vi addConstraints:contraints1];

[vi addConstraints:contraints2];