自定义UITextField，支持placeholderFont、placeholderColor、offset、isEnableDecimalLimit

• 使用方法

    self.textField = [[NBTextField alloc]initWithFrame:CGRectMake(0, 0, 400, 60)];
    [self.view addSubview:self.textField];
    self.textField.placeholder = @"请输入内容...";
    self.textField.offset = CGPointMake(20, 10);
    self.textField.placeholderColor = UIColor.lightGrayColor;
    self.textField.placeholderFont = [UIFont systemFontOfSize:20.0];
    UIView *leftView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 20, 20)];
    leftView.backgroundColor = UIColor.orangeColor;
    self.textField.leftView = leftView;
    self.textField.leftViewMode = UITextFieldViewModeAlways;
    self.textField.center = self.view.center;
    self.textField.backgroundColor = [UIColor colorWithHue:0.0 saturation:0.0 brightness:0.0 alpha:0.02];

• 源码分享

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface NBTextField : UITextField

/// 占位字体
@property (nonatomic, strong) UIFont *placeholderFont;
/// 占位字颜色
@property (nonatomic, strong) UIColor *placeholderColor;
/// 内边距偏移量
@property (nonatomic, assign) CGPoint offset;
/// 是否开启输入小数点后,仅支持两位数
@property (nonatomic, assign) BOOL isEnableDecimalLimit;

@end

NS_ASSUME_NONNULL_END

#import "NBTextField.h"
#import <objc/runtime.h>

@interface NBTextField() <UITextFieldDelegate>

@property (nonatomic, strong) UILabel *placeholderLabel;

@end

@implementation NBTextField

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.delegate = self;
        self.placeholderColor = UIColor.lightGrayColor;
        self.placeholderFont = [UIFont systemFontOfSize:17.0];
    }
    return self;
}

- (UILabel *)placeholderLabel {
    if (!_placeholderLabel) {
        Ivar ivar =  class_getInstanceVariable(UITextField.class, "_placeholderLabel");
        _placeholderLabel = object_getIvar(self, ivar);
    }
    return _placeholderLabel;
}

- (void)setPlaceholderFont:(UIFont *)placeholderFont {
    self.placeholderLabel.font = placeholderFont;
}

- (void)setPlaceholderColor:(UIColor *)placeholderColor {
    self.placeholderLabel.textColor = placeholderColor;
}

- (CGRect)rectForBounds:(CGRect)bounds {
    CGRect rect = bounds;
    
    CGFloat leftViewWidth = 0.0f;
    if (self.leftView) {
        leftViewWidth = self.leftView.bounds.size.width;
    }
    
    // 调整X坐标和宽度
    rect.origin.x += leftViewWidth + self.offset.x;
    rect.size.width -= leftViewWidth + fabs(self.offset.x);
    
    if (self.offset.x < 0) {
        rect.size.width = MIN(rect.size.width, bounds.size.width - leftViewWidth);
    }
    
    // 调整Y坐标
    rect.origin.y += self.offset.y;
    
    if (self.offset.y < 0) {
        rect.origin.y = MIN(rect.origin.y, bounds.origin.y);
    }
    
    return rect;
}

- (CGRect)placeholderRectForBounds:(CGRect)bounds {
    return [self rectForBounds:bounds];
}

- (CGRect)textRectForBounds:(CGRect)bounds {
    return [self rectForBounds:bounds];
}

- (CGRect)editingRectForBounds:(CGRect)bounds {
    return [self rectForBounds:bounds];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if (!self.isEnableDecimalLimit) {
        return YES;
    }

    NSString *currentText = [textField.text stringByReplacingCharactersInRange:range withString:string] ? : @"";
    
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", @"^$|^0$|^0\\.[0-9]{0,2}$|^[1-9][0-9]*\\.?[0-9]{0,2}$"];
    BOOL isValid = [predicate evaluateWithObject:currentText];

    return isValid;
}

@end