Question

我正试图增加一个积极/消极的纽芬兰语,以输入一个图形领域,但我不能让它正常运作。我想做的是,在数字投入的前面添加或删除一个消极迹象。我能够这样做,但我找不到一种方法,来维持原位数。这是我尝试的:

- (IBAction) negsign
{
    float input = [userinput.text floatValue];
    float result = ((input * (-1)));
    negstring = [NSString stringWithFormat:
                          @"%f", result];
    userinput.text = negstring;
}

之后,我只得到一幅零,如23.0万。我试图通过改用“%.2f”来限制小数点,但I dont想要为整批愤怒者增加零,或四舍五入2个小数点。我只想做像34.658939或23这样的事情,使之成为34.658939或23。是否有办法这样做?

Answer 1

在你看来,最能做的是以下法典:

float input = [userinput.text floatValue];
float result = ((input * (-1)));
NSNumber *resultNum = [NSNumber numberWithFloat:result];
NSString *resultString = [resultObj stringValue];
userinput.text = resultString;

如果你试图使数字成为负数而不是推翻签字,则最好替换<代码>float result = ((投入*-1)); with float result =-ABS(投入);。

Answer 2

事实上,解决这一问题的最佳途径是永远不会从表面上改变。仅以这种需要取代第一种性质:

- (IBAction) negsign
{
    unichar firstCharacter = [userinput.text characterAtIndex:0];
    if (firstCharacter ==  - ) {
        // Change the first character to a + sign.
        userinput.text = [userinput.text stringByReplacingCharactersInRange:NSMakeRange(0, 1) 
                                                                 withString:@"+"];
    } else if (firstCharacter ==  + ) {
        // Change the first character to a - sign.
        userinput.text = [userinput.text stringByReplacingCharactersInRange:NSMakeRange(0, 1) 
                                                                 withString:@"-"];
    } else {
        // There is no sign so we assume that it is positive.  
        // Insert the - at the beginning.
        userinput.text = [userinput.text stringByReplacingCharactersInRange:NSMakeRange(0, 0) 
                                                                 withString:@"-"];
    }
}

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