diff --git a/FittableFontLabel/.swiftlint.yml b/FittableFontLabel/.swiftlint.yml
index 79dedf9..9c5351b 100644
--- a/FittableFontLabel/.swiftlint.yml
+++ b/FittableFontLabel/.swiftlint.yml
@@ -1,3 +1,31 @@
 line_length: 180
+opt_in_rules:
+ - closure_spacing
+ - conditional_returns_on_newline
+ - empty_count
+ - explicit_init
+ - overridden_super_call
+ - redundant_nil_coalescing
+ - nimble_operator
+ - closure_end_indentation
+ - first_where
+ - attributes
+ - operator_usage_whitespace
+ - prohibited_super_call
+ - number_separator
+ - object_literal
+ - fatal_error_message
+ - private_outlet
+ - implicit_return
+ - multiline_parameters
+ - vertical_parameter_alignment_on_call
+ - unneeded_parentheses_in_closure_argument
+ - joined_default_parameter
+ - pattern_matching_keywords
+ - array_init
+ - contains_over_first_not_nil
+ - let_var_whitespace
+ - literal_expression_end_indentation
+ # - trailing_closure // false positive
 included:
  - ../Source
\ No newline at end of file
diff --git a/FittableFontLabel/Source/FittableFontLabel.swift b/FittableFontLabel/Source/FittableFontLabel.swift
index 31c7721..a51c2b9 100644
--- a/FittableFontLabel/Source/FittableFontLabel.swift
+++ b/FittableFontLabel/Source/FittableFontLabel.swift
@@ -24,7 +24,8 @@
 import UIKit
 
 // An UILabel subclass allowing you to automatize the process of adjusting the font size.
-@IBDesignable open class FittableFontLabel: UILabel {
+@IBDesignable
+open class FittableFontLabel: UILabel {
 
     // MARK: Properties
 
@@ -94,9 +95,9 @@ import UIKit
 
 // MARK: Helpers
 
-fileprivate extension FittableFontLabel {
+extension FittableFontLabel {
 
-    func adjustFontSize() {
+    private func adjustFontSize() {
         if autoAdjustFontSize {
             fontSizeToFit(maxFontSize: maxFontSize, minFontScale: minFontScale)
         }
diff --git a/FittableFontLabel/Source/UILabelExtension.swift b/FittableFontLabel/Source/UILabelExtension.swift
index 17d72b2..ba43078 100644
--- a/FittableFontLabel/Source/UILabelExtension.swift
+++ b/FittableFontLabel/Source/UILabelExtension.swift
@@ -53,7 +53,7 @@ public extension UILabel {
         let minFontScale = minFontScale.isNaN ? 0.1 : minFontScale
         let minimumFontSize = maxFontSize * minFontScale
         let rectSize = rectSize ?? bounds.size
-        guard string.count != 0 else {
+        guard !string.isEmpty else {
             return self.font.pointSize
         }
 
@@ -68,9 +68,9 @@ public extension UILabel {
 
 // MARK: - Helpers
 
-private extension UILabel {
+extension UILabel {
 
-    func currentAttributedStringAttributes() -> [NSAttributedStringKey: Any] {
+    private func currentAttributedStringAttributes() -> [NSAttributedStringKey: Any] {
         var newAttributes = [NSAttributedStringKey: Any]()
         attributedText?.enumerateAttributes(in: NSRange(0..<(text?.count ?? 0)), options: .longestEffectiveRangeNotRequired, using: { attributes, range, stop in
             newAttributes = attributes
@@ -82,13 +82,13 @@ private extension UILabel {
 
 // MARK: - Search
 
-private extension UILabel {
+extension UILabel {
 
-    enum FontSizeState {
-        case Fit, TooBig, TooSmall
+    private enum FontSizeState {
+        case fit, tooBig, tooSmall
     }
 
-    func binarySearch(string: String, minSize: CGFloat, maxSize: CGFloat, size: CGSize, constraintSize: CGSize) -> CGFloat {
+    private func binarySearch(string: String, minSize: CGFloat, maxSize: CGFloat, size: CGSize, constraintSize: CGSize) -> CGFloat {
         let fontSize = (minSize + maxSize) / 2
         var attributes = currentAttributedStringAttributes()
         attributes[NSAttributedStringKey.font] = font.withSize(fontSize)
@@ -101,7 +101,7 @@ private extension UILabel {
         let diff = maxSize - minSize
         guard diff > 0.1 else {
             switch state {
-            case .TooSmall:
+            case .tooSmall:
                 return maxSize
             default:
                 return minSize
@@ -109,33 +109,33 @@ private extension UILabel {
         }
 
         switch state {
-        case .Fit: return fontSize
-        case .TooBig: return binarySearch(string: string, minSize: minSize, maxSize: fontSize, size: size, constraintSize: constraintSize)
-        case .TooSmall: return binarySearch(string: string, minSize: fontSize, maxSize: maxSize, size: size, constraintSize: constraintSize)
+        case .fit: return fontSize
+        case .tooBig: return binarySearch(string: string, minSize: minSize, maxSize: fontSize, size: size, constraintSize: constraintSize)
+        case .tooSmall: return binarySearch(string: string, minSize: fontSize, maxSize: maxSize, size: size, constraintSize: constraintSize)
         }
     }
 
-    func singleLineSizeState(rect: CGRect, size: CGSize) -> FontSizeState {
+    private func singleLineSizeState(rect: CGRect, size: CGSize) -> FontSizeState {
         if rect.width >= size.width + 10 && rect.width <= size.width {
-            return .Fit
+            return .fit
         } else if rect.width > size.width {
-            return .TooBig
+            return .tooBig
         } else {
-            return .TooSmall
+            return .tooSmall
         }
     }
 
-    func multiLineSizeState(rect: CGRect, size: CGSize) -> FontSizeState {
+    private func multiLineSizeState(rect: CGRect, size: CGSize) -> FontSizeState {
         // if rect within 10 of size
         if rect.height < size.height + 10 &&
            rect.height > size.height - 10 &&
            rect.width > size.width + 10 &&
            rect.width < size.width - 10 {
-            return .Fit
+            return .fit
         } else if rect.height > size.height || rect.width > size.width {
-            return .TooBig
+            return .tooBig
         } else {
-            return .TooSmall
+            return .tooSmall
         }
     }
 
diff --git a/Source/FittableFontLabel.swift b/Source/FittableFontLabel.swift
index 31c7721..1c74911 100644
--- a/Source/FittableFontLabel.swift
+++ b/Source/FittableFontLabel.swift
@@ -24,7 +24,8 @@
 import UIKit
 
 // An UILabel subclass allowing you to automatize the process of adjusting the font size.
-@IBDesignable open class FittableFontLabel: UILabel {
+@IBDesignable
+open class FittableFontLabel: UILabel {
 
     // MARK: Properties
 
@@ -86,7 +87,7 @@ import UIKit
     // MARK: Insets
 
     open override func drawText(in rect: CGRect) {
-        let insets = UIEdgeInsets.init(top: topInset, left: leftInset, bottom: bottomInset, right: rightInset)
+        let insets = UIEdgeInsets(top: topInset, left: leftInset, bottom: bottomInset, right: rightInset)
         super.drawText(in: UIEdgeInsetsInsetRect(rect, insets))
     }
 
diff --git a/Source/UILabelExtension.swift b/Source/UILabelExtension.swift
index aa09816..2f75755 100644
--- a/Source/UILabelExtension.swift
+++ b/Source/UILabelExtension.swift
@@ -53,7 +53,7 @@ public extension UILabel {
         let minFontScale = minFontScale.isNaN ? 0.1 : minFontScale
         let minimumFontSize = maxFontSize * minFontScale
         let rectSize = rectSize ?? bounds.size
-        guard string.characters.count != 0 else {
+        guard !string.isEmpty else {
             return self.font.pointSize
         }