DRYUI

DRYUI is a tiny library that provides a better API for building and styling view hierarchies in code. DRYUI uses Masonry for Autolayout, and works on both iOS and OSX.

Installation

DRYUI is available through CocoaPods. To install it, just add the following line to your Podfile:

pod 'DRYUI'

##Hierarchy Building

To demonstrate, let's construct a simple view hierarchy, with 2 views nested inside self.view.

Building hierarchies normally

UIView *view1 = [UIView new];
view1.backgroundColor = [UIColor redColor];
[self.view addSubview:view1]
[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
    make.edges.equalTo(view1.superview);
}];

UIView *view2 = [UIView new];
view2.backgroundColor = [UIColor blueColor];
[view1 addSubview:view2];
[view2 mas_makeConstraints:^(MASConstraintMaker *make) {
    make.edges.equalTo(view1);
}];

Building hierarchies with DRYUI

build_subviews(self.view) {
    UIView *add_subview(view1) {
        _.backgroundColor = [UIColor redColor];
        make.edges.equalTo(superview);
        UIView *add_subview(view2) {
            _.backgroundColor = [UIColor blueColor];
            make.edges.equalTo(superview);
        };
    };
};

####Advantages:

• The hierarchy of the code mirrors the hierarchy of the views it creates - nested blocks correspond directly to nested subviews.
• Less repetitive boilerplate - no more forgetting to add your view as a subview.
• Less opportunity for copy-paste errors - since _ and superview are always bound to the current view, moving lines from one block to another automatically causes them to affect the view whose block they're moved to.
• Views are initialized for you - if you declare your subview as UIView, DRYUI will [[UIView alloc] init] it automagically.

##Styling

####Basics You can define a style like this:

in a .h file:

dryui_public_style(RedView);

and in the .m:

dryui_style(RedView) {
    _.backgroundColor = [UIColor redColor];
};

now you have a style named RedView that can be applied to views in add_subview like this:

build_subviews(self.view) {
    UIView *add_subview(thisViewIsRed, RedView) {
        // thisViewIsRed is now red.
    };
};

You can add any number of styles to a view in this way, and they'll be applied by calling the style blocks in the order they were added. The main block after add_subview runs after all styles have been applied, so it can override them.

If you want your style to be private to a .m file, then omit the dryui_public_style and use dryui_private_style in the .m:

dryui_private_style(RedView) {
    _.backgroundColor = [UIColor redColor];
};

####Styling for specific classes By default, style blocks assume they're being applied to UIViews. If you want to style a subclass of UIView, just add the class name as the second argument to dryui_style, dryui_public_style, or dryui_private_style:

dryui_style(RedButton, UIButton) {
    // _ is now a UIButton *
};

Attempting to apply a style like this to a view of the wrong type will trigger a compiler warning, and then a runtime exception.

####Style inheritance Styles also support simple inheritance like this:

dryui_style(RedView) {
    _.backgroundColor = [UIColor redColor];
};
dryui_style(RedAndWhiteLabel, UILabel) {
    dryui_parent_style(RedView);
    _.textColor = [UIColor whiteColor];
};
// Now, applying the RedAndWhiteLabel style to a UILabel will give it a red background and white text.

####Dynamic styles You can declare styles that take arguments, which you pass when the style is applied. The syntax looks like this:

dryui_style(ColorView, UIView, (UIColor *)colorArgument) {
    _.backgroundColor = colorArgument;
};

and then, to apply the style with arguments:

build_subviews(self.view) {
    UIView *add_subview(thisViewIsBlue, ColorView([UIColor blueColor])) {
        // thisViewIsBlue is now blue.
    };
};

Note that you must include the class that the style applies to, even if it's UIView.

Arguments are passed similarly when adding a parent style, or anywhere else the style is used:

dryui_style(TextAndBackgroundColor, UILabel, (UIColor *)textColor, (UIColor *)backgroundColor) {
    dryui_parent_style(ColorView(backgroundColor));
    _.textColor = textColor;
};

####Styles without build_subviews To apply a style outside of the context of build_subviews/add_subview, you can simply call dryui_apply_style or dryui_apply_styles with the view and styles you wish to apply:

UIView *view = [UIView new];
dryui_apply_style(view, RedView);

UIView *view = [UIView new];
dryui_apply_styles(view, RedView, ColorView([UIColor redColor]));

##Advanced Usage of add_subview:

add_subview takes as its first argument a variable name. If a variable of that name has already been declared, add_subview will initialize a new object of that variable's type and assign it to the variable. If it hasn't been declared, put the type you want the variable to have before add_subview and add_subview will declare the variable and assign to it. You can also have add_subview assign to a property by passing in self.propertyName.

add_subview can optionally take an instance of UIView as its second argument. If you call add_subview this way, then that instance will be assigned to the variable instead of the defualt [[<variable type> alloc] init] that happens otherwise.

After the first (and optional second) argument, a list of styles can be passed to add_subview to apply all the given styles to the view.

Here are some examples:

__block UIButton *secondButton, *thirdButton;
build_subviews(self) {
    UIButton *add_subview(firstButton) {};
    // The above line is equivalent to:
    //     UIButton *firstButton = [[UIButton alloc] init]; 
    //     [_ addSubview:firstButton];
    
    add_subview(secondButton) {};
    // secondButton has already been declared, to this is equivalent to:
    //     secondButton = [[UIButton alloc] init];
    //     [_ addSubview:secondButton];
    
    thirdButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    add_subview(thirdButton) {};
    // thirdButton has already been assigned, so this just does:
    //    [_ addSubview:thirdButton];
    
    UIButton *add_subview(fourthButton, [UIButton buttonWithType:UIButtonTypeSystem]) {};
    // The second argument to add_subview is a view instance, so we'll use it for assignment
    // instead of the default alloc init:
    //     UIButton *fourthButton = [UIButton buttonWithType:UIButtonTypeSystem];
    //     [_ addSubview:fourthButton];
    
    UIButton *add_subview(fifthButton, RedView, RedButton) {};
    // Simple style application - this will create a new button named fifthButton and
    // apply the RedView and RedButton styles to it.
    
    UIButton *add_subview(sixthButton, [UIButton buttonWithType:UIButtonTypeSystem], RedView, RedButton) {};
    // Style application with a custom view instance - add_subview can detect that its second argument
    // is a custom view instance instead of a style, so this will do:
    //     UIButton *sixthButton = [UIButton buttonWithType:UIButtonTypeSystem];
    //     [_ addSubview:sixthButton];
    // and then add the RedView and RedButton styles to sixthButton.
};

Each call to add_subview will add the given view as a subview to the view passed to the most recent nested call of build_subviews or add_subview. The order of views will be determined by the order of their add_subview calls.

Calls to add_subview must be inside a call to build_subviews. build_subviews won't add the given view as a subview to anything.

Within the block after the add_subview macro, _ refers to the given view, and superview refers to that view's superview. make is set to a MASConstraintMaker for the given view, similar to the block passed to Masonry's mas_makeConstraints: method.