[英]Why is my NSRange always 0?
我想为我的计算器应用实现删除键。 我为此的伪代码是:
foo = length of current number
bar = length of current number-1
current number = current number with character at index (foo-bar) removed
为了在Objective-C中做到这一点,我尝试使用NSRange函数以及StringbyappendingString方法来实现这一点:
- (IBAction)DelPressed {
if ([self.display.text length] >=2)
{
int len = [self.display.text length];//Length of entire display
//Add to the brainlong printing out the length of the entire display
self.brainlog.text = [NSString stringWithFormat:@"Len is %g",len];
int le = ([self.display.text length]-1);//Length of entire display - 1
NSString *lestring = [NSString stringWithFormat:@"LE is %g",le];
//Add to the brainlog printing out the length of the display -1
self.brainlog.text = [self.brainlog.text stringByAppendingString:lestring];
NSRange range = NSMakeRange(le, len);//range only includes the last character
self.display.text = [self.display.text stringByReplacingCharactersInRange:range withString:@" "];//Replace the last character with whitespace
}
脑力输出(即le和len的长度)为:
Len is -1.99164 Le is -1.99164
很难看到,但这是我使用iOS模拟器输入到计算器的数字的图像:
我试图更改le的值(即使它的显示长度为-3或-5等),而le和len仍然相同。
我还尝试使le引用len:
int len = [self.display.text length];//Length of entire display
//Add to the brainlong printing out the length of the entire display
self.brainlog.text = [NSString stringWithFormat:@"Len is %g",len];
int le = len-1;
但是两者的值仍然相同。 如何使用NSRange删除显示的最后一个字符?
编辑 :使用达斯汀的修复程序,我现在将相当冗长的函数缩减为6行代码:
-(IBAction)DelPressed{
if ([self.display.text length] >=2)
{
self.display.text = [self.display.text substringToIndes:[self.display.text length] -1];
}
}
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