一、前言
笔者最近一直忙于开发业务需求，频繁的使用着继承、分类，切身的体会到很多需求用这两种方案都可以解决，这就面临着幸福二选一的问题了！但越到后面，越能感觉到其明显的区别，于是有所感~
继承与分类
二、需求简要
iOS 时间选择器(UIDatePicker)大家都有用过吧，很方便对吧，那性别选择、省市区选择、付款方式选择等功能，我们如何实现类似的效果呢？用UIPickerView实现单选择功能，就能实现类似的用户体验。
三、应用场景
笔者最近遇到的开发需求是产品的属性选择，比如我们现在要发起订单（我们可以类比一下淘宝），选择了佳得乐，这时候我们还要选择口味（蓝莓、鲜橙、哈密瓜等），然后还可以选择净含量等。
demo
四、代码实现
由于在实际开发中，通常都是与UITextField联合实现的，笔者就选择UITextField为最小颗粒度，对其进行处理。
- 1.使用继承方案
LYTextField.h
#import <UIKit/UIKit.h>
@interface LYTextField : UITextField
@property (nonatomic, strong) NSArray *dataArr;
@end
LYTextField.m
#import "LYTextField.h"
@interface LYTextField ()
<UIPickerViewDelegate, UIPickerViewDataSource>
@property (nonatomic, weak) UIPickerView *pickerView;
@end
@implementation LYTextField
- (instancetype)init {
self = [super init];
if (self) {
[self configFoundation];
}
return self;
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
self = [super initWithCoder:aDecoder];
if (self) {
[self configFoundation];
}
return self;
}
- (instancetype)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
[self configFoundation];
}
return self;
}
- (void)configFoundation {
CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width;
UIView *optionView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, screenWidth, 44)];
optionView.backgroundColor = [UIColor orangeColor];
UIButton *cancelBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[cancelBtn setFrame:CGRectMake(0, 0, 70, 44)];
[cancelBtn setTitle:@"取消" forState:UIControlStateNormal];
[cancelBtn setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[cancelBtn.titleLabel setFont:[UIFont systemFontOfSize:17.0]];
[cancelBtn addTarget:self action:@selector(onClickCancelBtn) forControlEvents:UIControlEventTouchUpInside];
[optionView addSubview:cancelBtn];
UIButton *finishBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[finishBtn setFrame:CGRectMake(screenWidth - 70, 0, 70, 44)];
[finishBtn setTitle:@"完成" forState:UIControlStateNormal];
[finishBtn setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[finishBtn.titleLabel setFont:[UIFont systemFontOfSize:17.0]];
[finishBtn addTarget:self action:@selector(onClickFinishBtn) forControlEvents:UIControlEventTouchUpInside];
[optionView addSubview:finishBtn];
UILabel *titleL = [[UILabel alloc]initWithFrame:CGRectMake(screenWidth / 2.0 - 75.0, 0, 150, 44)];
titleL.textAlignment = NSTextAlignmentCenter;
titleL.text = @"请选择类型";
[optionView addSubview:titleL];
self.inputAccessoryView = optionView;
UIPickerView *pickerView = [[UIPickerView alloc] init];
pickerView.dataSource = self;
pickerView.delegate = self;
pickerView.backgroundColor = [UIColor whiteColor];
self.pickerView = pickerView;
self.inputView = pickerView;
}
- (void)onClickCancelBtn {
[self resignFirstResponder];
}
- (void)onClickFinishBtn {
NSInteger index = [self.pickerView selectedRowInComponent:0];
if (index < self.dataArr.count) {
self.text = self.dataArr[index];
}
[self resignFirstResponder];
}
#pragma mark - Picker view data source && delegate
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
return self.dataArr.count;
}
- (NSString *)pickerView:(UIPickerView *)pickerView
titleForRow:(NSInteger)row
forComponent:(NSInteger)component {
if (row < self.dataArr.count) {
return self.dataArr[row];
}
return @"";
}
@end
- 2.使用分类方案
UITextField+Tool.h
#import <UIKit/UIKit.h>
typedef void(^DidSelectedBlock)(NSString *value);
@interface UITextField (Tool)
<UIPickerViewDelegate, UIPickerViewDataSource>
- (void)configSigleChoiceWith:(NSArray *)preData completion:(DidSelectedBlock)completion;
- (void)configValue:(NSString *)value;
@end
UITextField+Tool.m
#import "UITextField+Tool.h"
#import <objc/runtime.h>
@interface UITextField ()
@property (nonatomic, strong) NSArray *choiceData;
@property (nonatomic, copy) DidSelectedBlock didSelectedBlock;
@end
NSString *const KeyChoiceData = @"KeyChoiceData";
NSString *const KeyDidSelectedBlock = @"KeyDidSelectedBlock";
@implementation UITextField (Tool)
- (NSArray *)choiceData {
return objc_getAssociatedObject(self, &KeyChoiceData);
}
- (void)setChoiceData:(NSArray *)choiceData {
objc_setAssociatedObject(self, &KeyChoiceData, choiceData, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (DidSelectedBlock)didSelectedBlock {
return objc_getAssociatedObject(self, &KeyDidSelectedBlock);
}
- (void)setDidSelectedBlock:(DidSelectedBlock)didSelectedBlock {
objc_setAssociatedObject(self, &KeyDidSelectedBlock, didSelectedBlock, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
- (void)configSigleChoiceWith:(NSArray *)preData completion:(DidSelectedBlock)completion {
self.choiceData = [preData mutableCopy];
self.didSelectedBlock = completion;
[self setSelectedList];
}
- (void)configValue:(NSString *)value {
self.text = value;
if (self.didSelectedBlock) {
self.didSelectedBlock(value);
}
if (value.length == 0) {
return;
}
for (NSInteger i = 0; i < self.choiceData.count; i ++) {
NSString *itemStr = self.choiceData[I];
if ([value isEqualToString:itemStr]) {
UIPickerView *pickerView = (UIPickerView *)self.inputView;
[pickerView selectRow:i inComponent:0 animated:YES];
break;
}
}
}
- (void)setSelectedList {
CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width;
UIView *optionView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, screenWidth, 44)];
optionView.backgroundColor = [UIColor orangeColor];
UIButton *cancelBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[cancelBtn setFrame:CGRectMake(0, 0, 70, 44)];
[cancelBtn setTitle:@"取消" forState:UIControlStateNormal];
[cancelBtn setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[cancelBtn.titleLabel setFont:[UIFont systemFontOfSize:17.0]];
[cancelBtn addTarget:self action:@selector(onClickCancelBtn) forControlEvents:UIControlEventTouchUpInside];
[optionView addSubview:cancelBtn];
UIButton *finishBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[finishBtn setFrame:CGRectMake(screenWidth - 70, 0, 70, 44)];
[finishBtn setTitle:@"完成" forState:UIControlStateNormal];
[finishBtn setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[finishBtn.titleLabel setFont:[UIFont systemFontOfSize:17.0]];
[finishBtn addTarget:self action:@selector(onClickFinishBtn) forControlEvents:UIControlEventTouchUpInside];
[optionView addSubview:finishBtn];
UILabel *titleL = [[UILabel alloc]initWithFrame:CGRectMake(screenWidth / 2.0 - 75.0, 0, 150, 44)];
titleL.textAlignment = NSTextAlignmentCenter;
titleL.text = @"请选择类型";
[optionView addSubview:titleL];
self.inputAccessoryView = optionView;
UIPickerView *pickerView = [[UIPickerView alloc] init];
pickerView.dataSource = self;
pickerView.delegate = self;
pickerView.backgroundColor = [UIColor whiteColor];
self.inputView = pickerView;
}
#pragma mark - Actions
- (void)onClickCancelBtn {
[self resignFirstResponder];
}
- (void)onClickFinishBtn {
UIPickerView *pickerView = (UIPickerView *)self.inputView;
NSInteger index = [pickerView selectedRowInComponent:0];
if (index < self.choiceData.count) {
[self configValue:self.choiceData[index]];
}
[self resignFirstResponder];
}
#pragma mark - Picker view data source && delegate
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
return self.choiceData.count;
}
- (NSString *)pickerView:(UIPickerView *)pickerView
titleForRow:(NSInteger)row
forComponent:(NSInteger)component {
if (row < self.choiceData.count) {
return self.choiceData[row];
}
return @"";
}
@end
- 3.使用代码
- (void)configTextFieldDemo {
CGFloat screenWidth = self.view.bounds.size.width;
LYTextField *textField1 = [[LYTextField alloc] init];
textField1.bounds = CGRectMake(0, 0, 200, 44);
textField1.borderStyle = UITextBorderStyleRoundedRect;
textField1.center = CGPointMake(screenWidth/2, 100);
textField1.placeholder = @"请选择口味";
textField1.dataArr = @[@"鲜橙", @"哈密瓜", @"蓝莓"];
[self.view addSubview:textField1];
UITextField *textField2 = [[UITextField alloc] init];
textField2.bounds = CGRectMake(0, 0, 200, 44);
textField2.borderStyle = UITextBorderStyleRoundedRect;
textField2.center = CGPointMake(screenWidth/2, 200);
textField2.placeholder = @"请选择净含量";
[self.view addSubview:textField2];
NSArray *dataArr = @[@"250 mL", @"500 mL", @"1000 mL"];
[textField2 configSigleChoiceWith:dataArr completion:nil];
}
五、写在最后
- 上例中，分类明显的优势在于可以孤立存在，也是最干净的编码。其实就是在一个对象的基础上增加额外的功能形成另外一个对象。
- 关于继承毫无疑问最大的优点是代码复用。但是很多时候继承也可能会被无止境的滥用，造成代码结构散乱，后期维护困难等，其中有可能带来最大的问题是高耦合，依赖性太强。
- 实际开发中如果继承超过2层的时候，就要慎重了，因为这可能是滥用继承的开始。
- 分类是一种平行的架构，相互独立存在，可移植性强，继承是纵向的架构，相互依赖，缺一个，整个架构就断层了。
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