[size=x-large]定义model file对象根据fiel对象的不同状态改变li样式
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[size=x-large]ok 搞定[/size]
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<li ng-class="{true:'z_step_bar_active',false:''}[file.step=='2'||file.step=='3']"></li>
[size=x-large]ok 搞定[/size]