Simple wrapper for VFL

gistfile1.m

// formula as 'width == width'
static NSLayoutConstraint*
_lcItemRel(UIView *v1, NSString *formula, UIView *v2, float ratio, float constant) {
    static NSDictionary *attrValueForName = nil;
    static dispatch_once_t attrOnceToken;
    dispatch_once(&attrOnceToken, ^{
        attrValueForName =
        @{
          @"left":      @(NSLayoutAttributeLeft),
          @"right":     @(NSLayoutAttributeRight),
          @"top":       @(NSLayoutAttributeTop),
          @"bottom":    @(NSLayoutAttributeBottom),
          @"leading":   @(NSLayoutAttributeLeading),
          @"trailing":  @(NSLayoutAttributeTrailing),
          @"width":     @(NSLayoutAttributeWidth),
          @"height":    @(NSLayoutAttributeHeight),
          @"centerX":   @(NSLayoutAttributeCenterX),
          @"centerY":   @(NSLayoutAttributeCenterY),
          @"baseline":  @(NSLayoutAttributeBaseline),
          };
    });
    
    static NSDictionary *relationValueForName = nil;
    static dispatch_once_t relationOnceToken;
    dispatch_once(&relationOnceToken, ^{
        relationValueForName =
        @{
          @"==":  @(NSLayoutRelationEqual),
          @">=":  @(NSLayoutRelationGreaterThanOrEqual),
          @"<=":  @(NSLayoutRelationLessThanOrEqual),
          };
    });
    
    NSArray *kv = [formula componentsSeparatedByString:@" "];
    
    NSLayoutAttribute a1, a2;
    NSLayoutRelation r;
    
    if (kv[0]==nil || kv[1]==nil || kv[2]==nil) {
        return nil;
    }
    
    a1 = (NSLayoutAttribute)[((NSNumber*)attrValueForName[kv[0]]) integerValue];
    a2 = (NSLayoutAttribute)[((NSNumber*)attrValueForName[kv[2]]) integerValue];
    r = (NSLayoutRelation)[((NSNumber*)relationValueForName[kv[1]]) integerValue];

    return [NSLayoutConstraint constraintWithItem:v1
                                        attribute:a1
                                        relatedBy:r
                                           toItem:v2
                                        attribute:a2
                                       multiplier:ratio
                                         constant:constant];
}

static NSArray*
_lcAryOfVFL(NSString *formula, NSLayoutFormatOptions opt, NSDictionary *metric, NSDictionary *views) {
    return [NSLayoutConstraint
            constraintsWithVisualFormat:formula
            options:opt
            metrics:metric
            views:views];
}