这是本人第一次写有关ios的博客，也不知道要写什么内容，所以先把自己随手弄的一个自定义View给搞上来，大家觉得好用的话也可以拿去用，后期我再优化一下，感觉在布局那块还是蛮好用的，当然，如果你们这群大神有更好的用法请通知我，我刚涉及ios不久。

在ios xib布局文件中，用自动布局约束的时候，UIView的宽和高最小只能设置1，而不能设置0.5之类的，然后在运行的时候会发现线条太粗，影响整体美观。

一般出现这种问题的时候我都会选择自己定义一条线条，然后就在项目上通用，如果是代码生成的UIView当线条的话，自然可以生成0.5宽高的线条，但是在自动布局约束的时候就没办法了，所以我基于约束布局的情况下定义的线条。

这里最重要的是在代码实现xib布局中的约束条件，针对约束这一块，我到时候会另外总结一篇文章出来，然后下面我就直接贴代码了，可以直接用，还封装得不是很好。具体我今天优化了一下，把上一次遗留的三个问题都解决了，然后用起来更加方便了

LineView.h

//
//  LineView.h
//  cafe
//
//  Created by xihao on 17/1/13.
//  Copyright © 2017年 yidont. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface LineView : UIView

//@property (nonatomic) BOOL isVertical;

@property (strong,nonatomic)IBOutlet NSString* key_direction;

@property (strong,nonatomic)IBOutlet UIColor * key_color;

//设置线条颜色
-(void)setLineColor:(UIColor*)color;

@end

LineView.m

//
//  LineView.m
//  cafe
//
//  Created by xihao on 17/1/13.
//  Copyright © 2017年 yidont. All rights reserved.
//

#import "LineView.h"

#define LINE_COLOR [UIColor colorWithRed:220/255.0f green:220/255.0f blue:220/255.0f alpha:1.0] //线条颜色

@implementation LineView{
    BOOL isVertical;
    UIView* lineV;
}

-(void)awakeFromNib{
    [super awakeFromNib];
    [self initView];
}


-(void)initView{

    NSLog(@"线条方向==%@",self.key_direction);

    CGRect frame=self.frame;

    NSLog(@"line_h=%i,w=%i,ww=%i",(int)frame.size.height,(int)frame.size.width,(int)SCREEN_W);



    NSArray* array=self.constraints;
    for(NSLayoutConstraint* constraint in array){
        if (constraint.firstAttribute == NSLayoutAttributeHeight) {
            isVertical=false;
        }
        if (constraint.firstAttribute == NSLayoutAttributeWidth) {
            isVertical=true;
        }
    }



    lineV=[[UIView alloc]init];
    lineV.translatesAutoresizingMaskIntoConstraints = NO;
    [self addSubview:lineV];



    if (isVertical) {

        NSLayoutConstraint *top=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTop multiplier:1 constant:0];
        top.active=YES;

        NSLayoutConstraint *bottom=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeBottom multiplier:1 constant:0];
        bottom.active=YES;

        NSLayoutConstraint *width=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeWidth multiplier:1 constant:0.5f];
        width.active=YES;


        if ([self.key_direction isEqualToString:@"left"]) {
            NSLayoutConstraint *leading=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeLeading multiplier:1 constant:0];
            leading.active=YES;
        }else if([self.key_direction isEqualToString:@"right"]){
            NSLayoutConstraint *trailing=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTrailing multiplier:1 constant:0];
            trailing.active=YES;
        }else{
            NSLayoutConstraint *centerX=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];
            centerX.active=YES;
        }

    }else{
        NSLayoutConstraint *leading=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeLeading multiplier:1 constant:0];
        leading.active=YES;

        NSLayoutConstraint *trailing=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTrailing multiplier:1 constant:0];
        trailing.active=YES;

        NSLayoutConstraint *height=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1 constant:0.5f];
        height.active=YES;


        if ([self.key_direction isEqualToString:@"top"]) {
            NSLayoutConstraint *top=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTop multiplier:1 constant:0];
            top.active=YES;
        }else if([self.key_direction isEqualToString:@"bottom"]){
            NSLayoutConstraint *bottom=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeBottom multiplier:1 constant:0];
            bottom.active=YES;
        }else{
            NSLayoutConstraint *centerY=[NSLayoutConstraint constraintWithItem:lineV attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];
            centerY.active=YES;
        }

    }
    if (self.key_color!=nil) {
        [lineV setBackgroundColor:self.key_color];
    }else{
        [lineV setBackgroundColor:LINE_COLOR];
    }


}


-(void)setLineColor:(UIColor *)color{
    [lineV setBackgroundColor:color];
}


@end